drm/amd/pm: add get enable mask function for smu v13_0_7

Add get_enabled_mask interface for smu v13_0_7.

Signed-off-by: Likun Gao <Likun.Gao@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>