drm/amd/pm: fix possible power mode mismatch between driver and PMFW

PMFW may boots the ASIC with a different power mode from the system's
real one. Notify PMFW explicitly the power mode the system in. This
is needed only when ACDC switch via gpio is not supported.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Kenneth Feng <kenneth.feng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org