drm/i915: Deobfuscate the render p-state obfuscation

The ironlake render p-state support includes some rather odd variable
names. Clean them up in order to improve the readability of the code.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 4a93f7a..9e80020 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4770,8 +4770,8 @@
 
 		if (obj_priv) {
 			I915_WRITE(PWRCTXA, obj_priv->gtt_offset | PWRCTX_EN);
-			I915_WRITE(RSTDBYCTL, I915_READ(RSTDBYCTL) &
-				   ~RCX_SW_EXIT);
+			I915_WRITE(MCHBAR_RENDER_STANDBY,
+				   I915_READ(MCHBAR_RENDER_STANDBY) & ~RCX_SW_EXIT);
 		}
 	}
 }