drm/amd/pm: update the gpu metrics data retrieving for Sienna Cichlid

Due to the structure layout change: "uint32_t ThrottlerStatus" -> "
uint8_t  ThrottlingPercentage[THROTTLER_COUNT]".

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>