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/image.c

@@ -155,6 +155,7 @@ static VAStatus copy_surface_to_image (struct request_data *driver_data,
 		return VA_STATUS_ERROR_INVALID_BUFFER;
 
 	for (i = 0; i < surface_object->destination_planes_count; i++) {
+#ifdef __arm__
 		if (!video_format_is_linear(driver_data->video_format))
 			tiled_to_planar(surface_object->destination_data[i],
 					buffer_object->data + image->offsets[i],
@@ -162,10 +163,13 @@ static VAStatus copy_surface_to_image (struct request_data *driver_data,
 					i == 0 ? image->height :
 						 image->height / 2);
 		else {
+#endif
 			memcpy(buffer_object->data + image->offsets[i],
 			       surface_object->destination_data[i],
 			       surface_object->destination_sizes[i]);
+#ifdef __arm__
 		}
+#endif
 	}
 
 	return VA_STATUS_SUCCESS;