drm/amd/display: Add debug option for allocating extra way for cursor

[Why and How]
- Add a debug option for allocating extra way for cursor
- Remove usage of cache_cursor_addr since it's not gaurenteed
  to be populated
- Include cursor size in MALL calculation if it exceeds the
  DCN cursor buffer size (and don't need extra way for cursor)

Reviewed-by: Aurabindo Pillai <Aurabindo.Pillai@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Alvin Lee <Alvin.Lee2@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>