drm/amd/pm: Fetch current power limit from FW

Power limit of SMUv13.0.6 SOCs can be updated by out-of-band ways. Fetch
the limit from firmware instead of using cached values.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Asad Kamal <asad.kamal@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org # 6.7.x