drm/amd/display: add workaround for subvp cursor corruption for DCN32/321

[Why&How]
Kernel does not have a means to tell the userspace to use software
cursor. Due to lack of this functionality, reducing the max cursor size
is the only way to ensure that power savings of Subview port feature is
utilized for asics that support it. The workaround could be removed
after cursor caching is fixed while a subviewport config is active.

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: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>