drm/amd/powerplay: unlock on error in smu_resume()

This function needs to drop the mutex before returning.

Fixes: f7e3a577 ("drm/amd/powerplay: check SMU engine readiness before proceeding on S3 resume")
Reviewed-by: Kevin Wang <kevin1.wang@amd.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/powerplay/amdgpu_smu.c

@@ -1384,7 +1384,7 @@ static int smu_resume(void *handle)
 	ret = smu_start_smc_engine(smu);
 	if (ret) {
 		pr_err("SMU is not ready yet!\n");
-		return ret;
+		goto failed;
 	}
 
 	ret = smu_smc_table_hw_init(smu, false);