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>