implement smu12 get_clk_freq interface to get clock frequency like
MCLK/SCLK.
Signed-off-by: NXiaomeng Hou <Xiaomeng.Hou@amd.com>
Reviewed-by: NHuang Rui <ray.huang@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>