GFX doorbell range should be set after flr otherwise the gfx doorbell
range will be overlap with MEC.

v2: remove "amdgpu_sriov_vf" and "amdgpu_in_reset" check, and add grbm
select for the case of 2 gfx rings.
Signed-off-by: Lin.Cao <lincao12@amd.com>
Acked-by: ZhenGuo Yin <zhenguo.yin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>