drm/i915: Introduce intel_uncore_unclaimed_mmio

Currently interrupt code is the only place checking
for the unclaimed register access prior to actual register
macros using the same functionality. Rename the function
and make it return bool so that the possible error message
context is clear in the caller side. The motivation is to allow
usage of unclaimed detection on arbitrary places.

v2: rebase, s/access/mmio, s/dev/dev_priv

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1450189512-30360-2-git-send-email-mika.kuoppala@intel.com

drivers/gpu/drm/i915/i915_irq.c

@@ -2190,7 +2190,8 @@ static irqreturn_t ironlake_irq_handler(int irq, void *arg)
 
 	/* We get interrupts on unclaimed registers, so check for this before we
 	 * do any I915_{READ,WRITE}. */
-	intel_uncore_check_errors(dev);
+	if (intel_uncore_unclaimed_mmio(dev_priv))
+		DRM_ERROR("Unclaimed register before interrupt\n");
 
 	/* disable master interrupt before clearing iir  */
 	de_ier = I915_READ(DEIER);