Fixes broken HW decoding. Root cause is missing kernel definitions supplied by
the rpi-5.10.y tree that are not mainlined; although linux-api-headers provides
the same file, e.g. /usr/include/linux/videodev2.h, the key definitions are
lacking.
Rather than creating another package[1] to supply kernel-api-headers built from
the rpi-5.10.y tree, we can define the missing defines directly in ffmpeg's
source via a patch. Credit to Dobroslaw Kijowski.
1. 481a5da6b3
