drm/amd/display: Dynamic cursor cache size for MALL eligibility check

[Why]
Currently we use the maximum possible cursor cache size when deciding if we
should attempt to enable MALL, but this prevents us from enabling the
feature for certain key use cases.

[How]
 - consider cursor bpp when calculating if the cursor fits

Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Joshua Aberback <joshua.aberback@amd.com>
Reviewed-by: Aric Cyr <aric.cyr@amd.com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>