drm/amd/display: Round cursor width up for MALL allocation

[Why & How]
When calculating cursor size for MALL allocation, the cursor width should
be the actual width rounded up to 64 alignment. Additionally, the bit
depth should vary depending on color format.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Alvin Lee <Alvin.Lee2@amd.com>
Acked-by: Pavle Kotarac <Pavle.Kotarac@amd.com>
Signed-off-by: Taimur Hassan <Syed.Hassan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>