drm/i915: Do gen5_gt_irq_postinstall() before enabling the master interrupt

Let's make sure the lower level interrupt bits are all lined
up before we flip on the master interrupt.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201021131443.25616-4-ville.syrjala@linux.intel.comReviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_irq.c

@@ -3474,11 +3474,11 @@ static void ilk_irq_postinstall(struct drm_i915_private *dev_priv)
 
 	ibx_irq_pre_postinstall(dev_priv);
 
+	gen5_gt_irq_postinstall(&dev_priv->gt);
+
 	GEN3_IRQ_INIT(uncore, DE, dev_priv->irq_mask,
 		      display_mask | extra_mask);
 
-	gen5_gt_irq_postinstall(&dev_priv->gt);
-
 	ilk_hpd_detection_setup(dev_priv);
 
 	ibx_irq_postinstall(dev_priv);