drm/ingenic: Silence uninitialized-variable warning

Silence compiler warning about used but uninitialized 'ipu_state'
variable. In practice, the variable would never be used when
uninitialized, but the compiler cannot know that 'priv->ipu_plane' will
always be NULL if CONFIG_INGENIC_IPU is disabled.

Silence the warning by initializing the value to NULL.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200719093834.14084-1-paul@crapouillou.net

drivers/gpu/drm/ingenic/ingenic-drm-drv.c

@@ -198,7 +198,7 @@ static int ingenic_drm_crtc_atomic_check(struct drm_crtc *crtc,
 					 struct drm_crtc_state *state)
 {
 	struct ingenic_drm *priv = drm_crtc_get_priv(crtc);
-	struct drm_plane_state *f1_state, *f0_state, *ipu_state;
+	struct drm_plane_state *f1_state, *f0_state, *ipu_state = NULL;
 	long rate;
 
 	if (!drm_atomic_crtc_needs_modeset(state))
@@ -229,7 +229,7 @@ static int ingenic_drm_crtc_atomic_check(struct drm_crtc *crtc,
 
 		/* If all the planes are disabled, we won't get a VBLANK IRQ */
 		priv->no_vblank = !f1_state->fb && !f0_state->fb &&
-				  !(priv->ipu_plane && ipu_state->fb);
+				  !(ipu_state && ipu_state->fb);
 	}
 
 	return 0;