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

This patch adds interface to parse pptable for smu.
It's to parse pptable format and fill PPTable_t smc_pptable to smu_table_context
structure. And read the smc_dpm_table from vbios, then fill it into smc_pptable.

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>