drm/amdgpu: use function pointer for gfxhub functions

gfxhub functions are now called from function pointers,
instead of from asic-specific functions.

Signed-off-by: Oak Zeng <Oak.Zeng@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amdgpu: add XGMI support for sienna cichlid

support for setting up XGMI FB address regions

Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: John Clements <john.clements@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amdgpu: add support gfxhub for sienna_cichlid (v3)

GFX10.3 is used for sienna_cichlid.

v2: squash in BANK_SELECT and FRAGMENT_SIZE fixes (Alex)
v3: squash in smallk update (Alex)

Signed-off-by: Likun Gao <Likun.Gao@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>