drm/amd/powerplay: add interface to write pptable (v2)

This patch adds interface to write pptable for smu.
It's to copy pptable bo in the vram to smc with SMU MSGs such as
SetDriverDramAddr and TransferTableDram2Smu.

v2: add detailed info to describe this function

Signed-off-by: Huang Rui <ray.huang@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>