add interface amdgpu_get_busy_percent for smu11

v2: convert data pointer type to uint32_t *.
Signed-off-by: NKevin Wang <Kevin1.Wang@amd.com>
Reviewed-by: NHuang Rui <ray.huang@amd.com>
Acked-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>