drm: mali-dp: potential dereference of null pointer

The return value of kzalloc() needs to be checked.
To avoid use of null pointer '&state->base' in case of the
failure of alloc.

Fixes: 99665d0 ("drm: mali-dp: add malidp_crtc_state struct")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Reviewed-by: Brian Starkey <brian.starkey@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211214100837.46912-1-jiasheng@iscas.ac.cn

drivers/gpu/drm/arm/malidp_crtc.c

@@ -487,7 +487,10 @@ static void malidp_crtc_reset(struct drm_crtc *crtc)
 	if (crtc->state)
 		malidp_crtc_destroy_state(crtc, crtc->state);
 
-	__drm_atomic_helper_crtc_reset(crtc, &state->base);
+	if (state)
+		__drm_atomic_helper_crtc_reset(crtc, &state->base);
+	else
+		__drm_atomic_helper_crtc_reset(crtc, NULL);
 }
 
 static int malidp_crtc_enable_vblank(struct drm_crtc *crtc)