The alignment of all the parameters in diff_bytes can be
anything the despite the documentation claiming otherwise.
8ecd3831 was based around
said documentation and is therefore insufficient to fix
e.g. the misaligned loads that happen in the huffyuvbgra
and huffyuvbgr24 vsynth FATE-tests.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>