drm: atmel-hlcdc: fix a NULL check

If kmalloc() returned NULL we would end up dereferencing "state" a
couple lines later.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c

@@ -414,7 +414,8 @@ atmel_hlcdc_crtc_duplicate_state(struct drm_crtc *crtc)
 		return NULL;
 
 	state = kmalloc(sizeof(*state), GFP_KERNEL);
-	if (state)
+	if (!state)
+		return NULL;
 	__drm_atomic_helper_crtc_duplicate_state(crtc, &state->base);
 
 	cur = drm_crtc_state_to_atmel_hlcdc_crtc_state(crtc->state);