drm/amdgpu: export amd_powerplay_func to amdgpu and other ip block

Update amdgpu to deal with the new powerplay module properly.

v2: squash in fixes
v3: squash in Rex's power state reporting fix

Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Acked-by: Jammy Zhou <Jammy.Zhou@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>