fourier-local: stateless control modernization + HEVC strip

Compound patch carrying the fork's pre-Step-1 substrate, originally
authored by Jernej Škrabec / fourier on top of bootlin's a3c2476:

- src/h264.c + src/picture.c: V4L2_CID_MPEG_VIDEO_H264_* renamed to
  V4L2_CID_STATELESS_H264_*, struct shapes tracked to mainline
  (V4L2_CID_STATELESS_H264_DECODE_MODE/_START_CODE added to the
  passthrough shim).
- include/hevc-ctrls.h: redirect shim to <linux/v4l2-controls.h>
  (kernel-side HEVC controls now live in the canonical UAPI header).
- src/meson.build: src/h265.c / src/h265.h commented out — HEVC
  build path is excluded from this fork (RK3568 hantro G1/G2 has
  no HEVC, and the kernel-side HEVC controls have a separate
  rework in flight upstream).
- src/tiled_yuv.S: aarch64 stub for tiled_to_planar (assembly
  source was sunxi-cedrus armv7-only; aarch64 needs a stub to keep
  the build linking).
- include/h264-ctrls.h: removed (dead post-fourier — no source
  includes it; the passthrough shim's CID aliases live in the
  kernel header now).

Functionally equivalent to the prior fork master commits:
  c1f5108 V4L2_PIX_FMT_H264_SLICE rename
  4ccbfe9 Strip HEVC build path
  da9f2a5 include/h264-ctrls.h passthrough + CID aliases
  fc4bb10 src/h264.c track upstream UAPI shape
  13e9b64 src/h264.c drop num_slices field
  4d14ffb src/tiled_yuv.S aarch64 stub
  1b02c9b src/h264.c include utils.h

Folded into one commit during 2026-05-04 Step 1 reconciliation
(see ../phase0_evidence/2026-05-04/findings.md). Per-patch history
of the early fork commits preserved on the pre-step1 branch.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/picture.c

@@ -51,6 +51,7 @@
 #include "autoconfig.h"
 
 static VAStatus codec_store_buffer(struct request_data *driver_data,
+				   struct object_context *context,
 				   VAProfile profile,
 				   struct object_surface *surface_object,
 				   struct object_buffer *buffer_object)
@@ -63,6 +64,14 @@ static VAStatus codec_store_buffer(struct request_data *driver_data,
 		 * RenderPicture), we can't use a V4L2 buffer directly
 		 * and have to copy from a regular buffer.
 		 */
+		if (context->h264_start_code) {
+			static const char start_code[3] = { 0x00, 0x00, 0x01 };
+
+			memcpy(surface_object->source_data +
+			       surface_object->slices_size,
+			       start_code, sizeof(start_code));
+			surface_object->slices_size += sizeof(start_code);
+		}
 		memcpy(surface_object->source_data +
 			       surface_object->slices_size,
 		       buffer_object->data,
@@ -184,16 +193,15 @@ static VAStatus codec_set_controls(struct request_data *driver_data,
 	case VAProfileH264ConstrainedBaseline:
 	case VAProfileH264MultiviewHigh:
 	case VAProfileH264StereoHigh:
-		rc = h264_set_controls(driver_data, context, surface_object);
+		rc = h264_set_controls(driver_data, context, profile,
+				       surface_object);
 		if (rc < 0)
 			return VA_STATUS_ERROR_OPERATION_FAILED;
 		break;
 
 	case VAProfileHEVCMain:
-		rc = h265_set_controls(driver_data, context, surface_object);
-		if (rc < 0)
-			return VA_STATUS_ERROR_OPERATION_FAILED;
-		break;
+		/* Fourier-local: HEVC stripped, no HW support on RK3566. */
+		return VA_STATUS_ERROR_UNSUPPORTED_PROFILE;
 
 	default:
 		return VA_STATUS_ERROR_UNSUPPORTED_PROFILE;
@@ -255,7 +263,8 @@ VAStatus RequestRenderPicture(VADriverContextP context, VAContextID context_id,
 		if (buffer_object == NULL)
 			return VA_STATUS_ERROR_INVALID_BUFFER;
 
-		rc = codec_store_buffer(driver_data, config_object->profile,
+		rc = codec_store_buffer(driver_data, context_object,
+					config_object->profile,
 					surface_object, buffer_object);
 		if (rc != VA_STATUS_SUCCESS)
 			return rc;