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/1467297225-21379-19-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_display.c

@@ -4486,7 +4486,9 @@ void hsw_disable_ips(struct intel_crtc *crtc)
 		WARN_ON(sandybridge_pcode_write(dev_priv, DISPLAY_IPS_CONTROL, 0));
 		mutex_unlock(&dev_priv->rps.hw_lock);
 		/* wait for pcode to finish disabling IPS, which may take up to 42ms */
-		if (wait_for((I915_READ(IPS_CTL) & IPS_ENABLE) == 0, 42))
+		if (intel_wait_for_register(dev_priv,
+					    IPS_CTL, IPS_ENABLE, 0,
+					    42))
 			DRM_ERROR("Timed out waiting for IPS disable\n");
 	} else {
 		I915_WRITE(IPS_CTL, 0);