drm/i915: Drop I915_ prefix from HAS_FBC

My OCD just couldn't let this slide. Spotted while reviewing Ville's
patch to only flip planes when we have FBC.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 5344599..26e6d1b 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -461,7 +461,7 @@
 	const struct drm_display_mode *adjusted_mode;
 	unsigned int max_width, max_height;
 
-	if (!I915_HAS_FBC(dev)) {
+	if (!HAS_FBC(dev)) {
 		set_no_fbc_reason(dev_priv, FBC_UNSUPPORTED);
 		return;
 	}
@@ -5541,7 +5541,7 @@
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	if (I915_HAS_FBC(dev)) {
+	if (HAS_FBC(dev)) {
 		if (INTEL_INFO(dev)->gen >= 7) {
 			dev_priv->display.fbc_enabled = ironlake_fbc_enabled;
 			dev_priv->display.enable_fbc = gen7_enable_fbc;