drm/i915: Remove NULL dev_priv checks from irq_uninstall

There should be no way to land in irq_uninstall without a
valid dev_priv. Let's kill off the remaining checks, which are
probably some kind of UMS leftovers. Not all the irq_uninstall
hooks even had them anymore.
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170818183705.27850-10-ville.syrjala@linux.intel.com

drivers/gpu/drm/i915/i915_irq.c

@@ -3544,11 +3544,6 @@ static int cherryview_irq_postinstall(struct drm_device *dev)
 
 static void gen8_irq_uninstall(struct drm_device *dev)
 {
-	struct drm_i915_private *dev_priv = to_i915(dev);
-
-	if (!dev_priv)
-		return;
-
 	gen8_irq_reset(dev);
 }
 
@@ -3556,9 +3551,6 @@ static void valleyview_irq_uninstall(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = to_i915(dev);
 
-	if (!dev_priv)
-		return;
-
 	I915_WRITE(VLV_MASTER_IER, 0);
 	POSTING_READ(VLV_MASTER_IER);
 
@@ -3576,9 +3568,6 @@ static void cherryview_irq_uninstall(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = to_i915(dev);
 
-	if (!dev_priv)
-		return;
-
 	I915_WRITE(GEN8_MASTER_IRQ, 0);
 	POSTING_READ(GEN8_MASTER_IRQ);
 
@@ -3594,11 +3583,6 @@ static void cherryview_irq_uninstall(struct drm_device *dev)
 
 static void ironlake_irq_uninstall(struct drm_device *dev)
 {
-	struct drm_i915_private *dev_priv = to_i915(dev);
-
-	if (!dev_priv)
-		return;
-
 	ironlake_irq_reset(dev);
 }
 
@@ -4103,9 +4087,6 @@ static void i965_irq_uninstall(struct drm_device * dev)
 {
 	struct drm_i915_private *dev_priv = to_i915(dev);
 
-	if (!dev_priv)
-		return;
-
 	i915_hotplug_interrupt_update(dev_priv, 0xffffffff, 0);
 	I915_WRITE(PORT_HOTPLUG_STAT, I915_READ(PORT_HOTPLUG_STAT));