gpu/drm: Ingenic: Fix opaque pointer casted to wrong type

The opaque pointer passed to the IRQ handler is a pointer to the
drm_device, not a pointer to our ingenic_drm structure.

It still worked, because our ingenic_drm structure contains the
drm_device as its first field, so the pointer received had the same
value, but this was not semantically correct.

Cc: stable@vger.kernel.org # v5.3
Fixes: 90b86fcc ("DRM: Add KMS driver for the Ingenic JZ47xx SoCs")
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20200516215057.392609-5-paul@crapouillou.netAcked-by: Sam Ravnborg <sam@ravnborg.org>

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

@@ -474,7 +474,7 @@ static int ingenic_drm_encoder_atomic_check(struct drm_encoder *encoder,
 
 static irqreturn_t ingenic_drm_irq_handler(int irq, void *arg)
 {
-	struct ingenic_drm *priv = arg;
+	struct ingenic_drm *priv = drm_device_get_priv(arg);
 	unsigned int state;
 
 	regmap_read(priv->map, JZ_REG_LCD_STATE, &state);