drm/amd/pm: correct the power limits reporting on OOB supported

As OOB(out-of-band) interface may be used to update the power limits.
Thus to make sure the power limits reporting of our driver always
reflects the correct values, the internal cache must be aligned
carefully.

V2: add support for out-of-band of other ASICs
    align cached current power limit with OOB imposed

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-By: Harish Kasiviswanathan <Harish.Kasiviswanathan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>