drm/arm/malidp: Fix possible dereference of NULL

There is possible deference of NULL pointer on return of
malidp_duplicate_plane_state() if kmalloc fails. Check the
returned kmalloc pointer before continuing.
Signed-off-by: Shailendra Verma <Shailendra.v@samsung.com>
[cleaned up the code and re-formatted the commit message]
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>

drivers/gpu/drm/arm/malidp_planes.c

@@ -67,13 +67,14 @@ drm_plane_state *malidp_duplicate_plane_state(struct drm_plane *plane)
 		return NULL;
 
 	state = kmalloc(sizeof(*state), GFP_KERNEL);
-	if (state) {
+	if (!state)
+		return NULL;
+
 	m_state = to_malidp_plane_state(plane->state);
 	__drm_atomic_helper_plane_duplicate_state(plane, &state->base);
 	state->rotmem_size = m_state->rotmem_size;
 	state->format = m_state->format;
 	state->n_planes = m_state->n_planes;
-	}
 
 	return &state->base;
 }