drm/amdgpu: enable umc 8.7 functions in gmc v10

add support for umc 8.7 initialization

add umc 8.7 source to makefile

Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Signed-off-by: John Clements <john.clements@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>