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

This patch adds interface to check pptable function for smu.
It's to check if the format_revision in vbios is up to pptable header version,
and the structure size is not 0.

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>