drm/radeon/dpm: fix uninitialized read from stack in kv_dpm_late_enable

If we take the false branch of the if quoted in the diff below, we
end up doing a return ret, without ever having initialized it.

Picked up by coverity.
Signed-off-by: Dave Jones <davej@fedoraproject.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/kv_dpm.c

@@ -1223,7 +1223,7 @@ int kv_dpm_enable(struct radeon_device *rdev)
 
 int kv_dpm_late_enable(struct radeon_device *rdev)
 {
-	int ret;
+	int ret = 0;
 
 	if (rdev->irq.installed &&
 	    r600_is_internal_thermal_sensor(rdev->pm.int_thermal_type)) {