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/1467297225-21379-45-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_psr.c

@@ -591,14 +591,20 @@ static void intel_psr_work(struct work_struct *work)
 	 * and be ready for re-enable.
 	 */
 	if (HAS_DDI(dev_priv)) {
-		if (wait_for((I915_READ(EDP_PSR_STATUS_CTL) &
-			      EDP_PSR_STATUS_STATE_MASK) == 0, 50)) {
+		if (intel_wait_for_register(dev_priv,
+					    EDP_PSR_STATUS_CTL,
+					    EDP_PSR_STATUS_STATE_MASK,
+					    0,
+					    50)) {
 			DRM_ERROR("Timed out waiting for PSR Idle for re-enable\n");
 			return;
 		}
 	} else {
-		if (wait_for((I915_READ(VLV_PSRSTAT(pipe)) &
-			      VLV_EDP_PSR_IN_TRANS) == 0, 1)) {
+		if (intel_wait_for_register(dev_priv,
+					    VLV_PSRSTAT(pipe),
+					    VLV_EDP_PSR_IN_TRANS,
+					    0,
+					    1)) {
 			DRM_ERROR("Timed out waiting for PSR Idle for re-enable\n");
 			return;
 		}