drm/amd/pp: Lock pm_funcs when set pp table

unlock mutex until set pp table completely to avoid
conflict if other pp functions were called simultaneously.

use hwmgr_handle_task instand of pp_dpm_dispatch_tasks.
It is not make sense that call pp_functions in ip_functions.

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