drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register()

By using the out-of-line intel_wait_for_register() not only do we can
efficiency from using the hybrid wait_for() contained within, but we
avoid code bloat from the numerous inlined loops, in total (all patches):

   text    data     bss     dec     hex filename
1078551    4557     416 1083524  108884 drivers/gpu/drm/i915/i915.ko
1070775    4557     416 1075748  106a24 drivers/gpu/drm/i915/i915.ko
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1467297225-21379-39-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_i2c.c

@@ -298,15 +298,16 @@ gmbus_wait_idle(struct drm_i915_private *dev_priv)
 {
 	int ret;
 
-#define C ((I915_READ_NOTRACE(GMBUS2) & GMBUS_ACTIVE) == 0)
-
 	if (!HAS_GMBUS_IRQ(dev_priv))
-		return wait_for(C, 10);
+		return intel_wait_for_register(dev_priv,
+					       GMBUS2, GMBUS_ACTIVE, 0,
+					       10);
 
 	/* Important: The hw handles only the first bit, so set only one! */
 	I915_WRITE(GMBUS4, GMBUS_IDLE_EN);
 
-	ret = wait_event_timeout(dev_priv->gmbus_wait_queue, C,
+	ret = wait_event_timeout(dev_priv->gmbus_wait_queue,
+				 (I915_READ_NOTRACE(GMBUS2) & GMBUS_ACTIVE) == 0,
 				 msecs_to_jiffies_timeout(10));
 
 	I915_WRITE(GMBUS4, 0);
@@ -315,7 +316,6 @@ gmbus_wait_idle(struct drm_i915_private *dev_priv)
 		return 0;
 	else
 		return -ETIMEDOUT;
-#undef C
 }
 
 static int