This patch adds get clock by type with latency, display will use it to get
current clocks with latency.

v2: fix the missed mutex lock before return.
Signed-off-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>