drm/amd/pm: adjust the visibility of pp_table sysfs node

drm/amd/pm: adjust the visibility of pp_table sysfs node

v1:
- make pp_table invisible on VF mode (only valid on BM)
- make pp_table invisible on Mi* chips (Not supported)
- make pp_table invisible if scpm feature is enabled.

v2:
move pp_table invisible code logic into amdgpu_dpm_get_pp_table() function.

v3:
add table buffer pointer check both on powerplay & swsmu.

Signed-off-by: Yang Wang <kevinyang.wang@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>