drm/amdgpu: Indirect register access for Navi12 sriov

This patch series are used for GC/MMHUB(part)/IH_RB_CNTL
indirect access in the SRIOV environment.

There are 4 bits, controlled by host, to control
if GC/MMHUB(part)/IH_RB_CNTL indirect access enabled.
(one bit is master bit controls other 3 bits)

For GC registers, changing all the register access from MMIO to
RLC and use RLC as the default access method in the full access time.

For partial MMHUB registers, changing their access from MMIO to
RLC in the full access time, the remaining registers
keep the original access method.

For IH_RB_CNTL register, changing it's access from MMIO to PSP.

Signed-off-by: Peng Ju Zhou <PengJu.Zhou@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>