This is the equivalent change for cuviddec after the previous change
for nvdec. I made similar changes to the copying routines to handle
pixel formats in a more generic way.

Note that unlike with nvdec, there is no confusion about the ability
of a codec to output 444 formats. This is because the cuvid parser is
used, meaning that 444 JPEG content is still indicated as using a 420
output format.