drm/vkms: add 3x4 matrix in color pipeline

drm/vkms: add 3x4 matrix in color pipeline

We add two 3x4 matrices into the VKMS color pipeline. The reason
we're adding matrices is so that we can test that application
of a matrix and its inverse yields an output equal to the input
image.

One complication with the matrix implementation has to do with
the fact that the matrix entries are in signed-magnitude fixed
point, whereas the drm_fixed.h implementation uses 2s-complement.
The latter one is the one that we want for easy addition and
subtraction, so we convert all entries to 2s-complement.

Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Signed-off-by: Simon Ser <contact@emersion.fr>
Link: https://patch.msgid.link/20251115000237.3561250-21-alex.hung@amd.com