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/1467297225-21379-44-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_psr.c

@@ -531,9 +531,11 @@ static void hsw_psr_disable(struct intel_dp *intel_dp)
 			   I915_READ(EDP_PSR_CTL) & ~EDP_PSR_ENABLE);
 
 		/* Wait till PSR is idle */
-		if (_wait_for((I915_READ(EDP_PSR_STATUS_CTL) &
-			       EDP_PSR_STATUS_STATE_MASK) == 0,
-			       2 * USEC_PER_SEC, 10 * USEC_PER_MSEC))
+		if (intel_wait_for_register(dev_priv,
+					    EDP_PSR_STATUS_CTL,
+					    EDP_PSR_STATUS_STATE_MASK,
+					    0,
+					    2000))
 			DRM_ERROR("Timed out waiting for PSR Idle State\n");
 
 		dev_priv->psr.active = false;