drm/i915: Fix irq checks in ring->irq_get/put functions

Yet another place that wasn't properly transformed when implementing
SOix. While at it convert the checks to WARN_ON on gen5+ (since we
don't have UMS potentially doing stupid things on those platforms).
And also add the corresponding checks to the put functions (again with
a WARN_ON) for gen5+.

v2: Drop the WARNINGS in the irq_put functions (including the existing
one for vebox), Chris convinced me that they're not that terribly
useful.

v3: Don't forget about execlist code.

Cc: Imre Deak <imre.deak@intel.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: "Volkin, Bradley D" <bradley.d.volkin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index bafd38b..803fc38 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1063,7 +1063,7 @@
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	unsigned long flags;
 
-	if (!dev->irq_enabled)
+	if (WARN_ON(!intel_irqs_enabled(dev_priv)))
 		return false;
 
 	spin_lock_irqsave(&dev_priv->irq_lock, flags);