drm/amd/powerplay: refine powerplay interface.

v2: add pp_check function to check pp_instance
   valid.

1. powerplay export two new interface to amdgpu,
   amd_powerplay_create/amd_powerplay_destroy.
2. create pp_instance/smumgr/hwmgr/eventmgr in
   early init, destroy them when lata_fini.
3. in sw_init, create and init asic private smumgr
   data, and free them when sw_fini.
4. in hw_init, create and init asic private hwmgr
   data, and free them when hw_fini.
5. export powerplay state: PP_DPM_DISABLED.
   when user disabled powerplay or hwmgr/eventmgr
   init failed, powerplay return this state to amdgpu.

Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>