ffmpeg-v4l2-request-fourier: patch NV15→P010 unpack for Hi10P / Main10

The n8.1 pin's hwcontext_v4l2request.c deliberately blanks the
transfer-formats list for AV_PIX_FMT_YUV420P10 sw_format (the mapping
target for V4L2_PIX_FMT_NV15), so `ffmpeg -hwaccel v4l2request
-vf hwdownload,format=p010le` on a Hi10P / Main10 input failed at
filter-init with -22 EINVAL — even though kernel-side decode succeeded.

0002-nv15-to-p010-unpack.patch adds an inline NV15→P010 unpack
(5 bytes per 4 samples, little-endian → high-10-of-16) inside
v4l2request_transfer_data_from, exposes AV_PIX_FMT_P010 in
transfer_get_formats for that sw_format, and rejects non-P010
destinations explicitly with ENOSYS instead of silently corrupting
output via av_frame_copy on NV15-packed bytes.

Verified on fresnel (RK3399, linux-fresnel-fourier 7.0-14):
- 5-frame smoke test from issue #21 → exit 0, 13.8MB output
- 20-frame mid-fixture decode → bit-exact HW==SW
  sha256 7d9b66d48d8f17b2281da1881c663ecc31722bb218aba1ae23bf28d07aa66b08
- 8-bit baseline (bbb_60s_720p.h264.mp4) still bit-exact HW==SW (no
  regression in the existing NV12 path)
- Cross-device repro of original EINVAL on unpatched ampere (RK3588)
  pkgrel=4, confirming the bug is upstream-FFmpeg-side, not RK3399-specific

Patch is upstream-able to Kwiboo's v4l2-request-n8.1 branch.

Closes #21.

arch/ffmpeg-v4l2-request-fourier/PKGBUILD

@@ -24,7 +24,7 @@ _srcname=FFmpeg
 _version='8.1'
 _commit='b57fbbe50c9b2656fad86a1a7eeabfd2b2a50935'  # v4l2-request-n8.1 tip 2026-04-24
 pkgver=8.1.r123329.b57fbbe
-pkgrel=4
+pkgrel=5
 epoch=2
 pkgdesc='FFmpeg with V4L2 Request API hwaccel (Rockchip / Allwinner stateless decode)'
 arch=('aarch64')
@@ -78,8 +78,9 @@ provides=(
 conflicts=(ffmpeg)
 replaces=(ffmpeg ffmpeg-v4l2-request-git)
 source=("git+https://github.com/Kwiboo/FFmpeg.git#commit=${_commit}"
-        '0001-libudev-bypass-fallback.patch')
-sha256sums=('SKIP' 'SKIP')
+        '0001-libudev-bypass-fallback.patch'
+        '0002-nv15-to-p010-unpack.patch')
+sha256sums=('SKIP' 'SKIP' 'SKIP')
 
 pkgver() {
   cd "${_srcname}"
@@ -91,6 +92,7 @@ pkgver() {
 prepare() {
   cd "${_srcname}"
   patch -Np1 -i "${srcdir}/0001-libudev-bypass-fallback.patch"
+  patch -Np1 -i "${srcdir}/0002-nv15-to-p010-unpack.patch"
 }
 
 build() {