drm/i915: remove unused leftover variable irq_received

It's been there since i8xx_irq_handler() was added in
commit c2798b19
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Sun Apr 22 21:13:57 2012 +0100

    drm/i915: i8xx interrupt handler
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_irq.c

@@ -2403,7 +2403,6 @@ static irqreturn_t i8xx_irq_handler(int irq, void *arg)
 	u16 iir, new_iir;
 	u32 pipe_stats[2];
 	unsigned long irqflags;
-	int irq_received;
 	int pipe;
 	u16 flip_mask =
 		I915_DISPLAY_PLANE_A_FLIP_PENDING_INTERRUPT |
@@ -2437,7 +2436,6 @@ static irqreturn_t i8xx_irq_handler(int irq, void *arg)
 					DRM_DEBUG_DRIVER("pipe %c underrun\n",
 							 pipe_name(pipe));
 				I915_WRITE(reg, pipe_stats[pipe]);
-				irq_received = 1;
 			}
 		}
 		spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);