[Why]
Implement an interface to obtain plane size caps

[How]
Add min_width, min_height fields to dc_plane_cap structure.
Set values to 16x16 for discrete ASICs, and 64x64 for others.
Signed-off-by: Igor Kravchenko <Igor.Kravchenko@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>