drm/amd/pm: update smartshift powerboost calc for smu12

smartshift apu and dgpu power boost are reported as percentage with
respect to their power limits. This value[0-100] reflects the boost
for the respective device.

Signed-off-by: Sathishkumar S <sathishkumar.sundararaju@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>