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/1467297225-21379-50-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_runtime_pm.c

@@ -703,8 +703,11 @@ static void skl_set_power_well(struct drm_i915_private *dev_priv,
 
 	switch (power_well->data) {
 	case SKL_DISP_PW_1:
-		if (wait_for((I915_READ(SKL_FUSE_STATUS) &
-			SKL_FUSE_PG0_DIST_STATUS), 1)) {
+		if (intel_wait_for_register(dev_priv,
+					    SKL_FUSE_STATUS,
+					    SKL_FUSE_PG0_DIST_STATUS,
+					    SKL_FUSE_PG0_DIST_STATUS,
+					    1)) {
 			DRM_ERROR("PG0 not enabled\n");
 			return;
 		}