drm/amdgpu: fix ref count leak in amdgpu_driver_open_kms

in amdgpu_driver_open_kms the call to pm_runtime_get_sync increments the
counter even in case of failure, leading to incorrect
ref count. In case of failure, decrement the ref count before returning.
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c

@@ -992,7 +992,7 @@ int amdgpu_driver_open_kms(struct drm_device *dev, struct drm_file *file_priv)
 
 	r = pm_runtime_get_sync(dev->dev);
 	if (r < 0)
-		return r;
+		goto pm_put;
 
 	fpriv = kzalloc(sizeof(*fpriv), GFP_KERNEL);
 	if (unlikely(!fpriv)) {
@@ -1043,6 +1043,7 @@ int amdgpu_driver_open_kms(struct drm_device *dev, struct drm_file *file_priv)
 
 out_suspend:
 	pm_runtime_mark_last_busy(dev->dev);
+pm_put:
 	pm_runtime_put_autosuspend(dev->dev);
 
 	return r;