drm/i915: Optimize DIV_ROUND_CLOSEST call

DIV_ROUND_CLOSEST is faster if the compiler knows it will only be
dealing with unsigned dividends. This optimization rips 32 bytes of
binary code on x86_64.
Signed-off-by: NJean Delvare <khali@linux-fr.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -2552,7 +2552,8 @@ static void gen6_update_ring_freq(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int min_freq = 15;
-	int gpu_freq, ia_freq, max_ia_freq;
+	int gpu_freq;
+	unsigned int ia_freq, max_ia_freq;
 	int scaling_factor = 180;
 
 	WARN_ON(!mutex_is_locked(&dev_priv->rps.hw_lock));