drm/amdgpu/powerplay: add a new interface to set the mp1 state

This is required for certain cases such as various GPU resets
(mode1, mode2), BACO, shutdown, unload, etc. to put the SMU into
the appropriate state for when the hw is re-initialized.

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