BACKPORT: media: v4l2: Add description for V4L2_PIX_FMT_AV1 in v4l_fill_fmtdesc()

Add a descriptive string for the AV1 pixel format to v4l_fill_fmtdesc(),
enabling proper reporting of AV1 support via VIDIOC_ENUM_FMT.

Link: https://lore.kernel.org/all/20251210-av1d_stateful_v3-v10-2-cf4379a3dcff@oss.qualcomm.com/
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: Hans Verkuil <hverkuil+cisco@kernel.org>
Signed-off-by: Deepa Guthyappa Madivalara <deepa.madivalara@oss.qualcomm.com>
Tested-by: Val Packett <val@packett.cool>
Signed-off-by: Bryan O'Donoghue <bod@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
(cherry picked from commit 1510965)

Author: dmadival

drivers/media/v4l2-core/v4l2-ioctl.c

@@ -1542,6 +1542,7 @@ static void v4l_fill_fmtdesc(struct v4l2_fmtdesc *fmt)
 		case V4L2_PIX_FMT_QC10C:	descr = "QCOM Compressed 10-bit Format"; break;
 		case V4L2_PIX_FMT_AJPG:		descr = "Aspeed JPEG"; break;
 		case V4L2_PIX_FMT_AV1_FRAME:	descr = "AV1 Frame"; break;
+		case V4L2_PIX_FMT_AV1:		descr = "AV1 OBU Stream"; break;
 		case V4L2_PIX_FMT_MT2110T:	descr = "Mediatek 10bit Tile Mode"; break;
 		case V4L2_PIX_FMT_MT2110R:	descr = "Mediatek 10bit Raster Mode"; break;
 		case V4L2_PIX_FMT_HEXTILE:	descr = "Hextile Compressed Format"; break;