vaapi: Scrambled rendering for some h.264 videos with glimagesink on AMD GPU

Submitted by Philippe Normand @philn

Link to original bug (#796584)

Description

vainfo:

libva info: VA-API version 1.1.0
libva info: va_getDriverName() returns 0
libva info: Trying to open /usr/lib/x86_64-linux-gnu/dri/radeonsi_drv_video.so
libva info: Found init function __vaDriverInit_1_1
libva info: va_openDriver() returns 0
vainfo: VA-API version: 1.1 (libva 2.1.0)
vainfo: Driver version: mesa gallium vaapi
vainfo: Supported profile and entrypoints
VAProfileMPEG2Simple : VAEntrypointVLD
VAProfileMPEG2Main : VAEntrypointVLD
VAProfileVC1Simple : VAEntrypointVLD
VAProfileVC1Main : VAEntrypointVLD
VAProfileVC1Advanced : VAEntrypointVLD
VAProfileH264ConstrainedBaseline: VAEntrypointVLD
VAProfileH264ConstrainedBaseline: VAEntrypointEncSlice
VAProfileH264Main : VAEntrypointVLD
VAProfileH264Main : VAEntrypointEncSlice
VAProfileH264High : VAEntrypointVLD
VAProfileH264High : VAEntrypointEncSlice
VAProfileHEVCMain : VAEntrypointVLD
VAProfileHEVCMain10 : VAEntrypointVLD
VAProfileJPEGBaseline : VAEntrypointVLD
VAProfileNone : VAEntrypointVideoProc

Scrambled rendering with: https://download.blender.org/durian/trailer/Sintel_Trailer.480p.DivX_Plus_HD.mkv

No rendering issue with: https://trac.webkit.org/export/232834/webkit/trunk/LayoutTests/media/content/test.mp4