drm/i915: Simplify _STATE_ debug macros

Take advantage of WARN return value to simplify the flow.

Cc: Rob Clark <robdclark@gmail.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reported-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1450441647-23924-2-git-send-email-joonas.lahtinen@linux.intel.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -88,23 +88,18 @@
  */
 #define I915_STATE_WARN(condition, format...) ({			\
 	int __ret_warn_on = !!(condition);				\
-	if (unlikely(__ret_warn_on)) {					\
-		if (i915.verbose_state_checks)				\
-			WARN(1, format);				\
-		else 							\
+	if (unlikely(__ret_warn_on))					\
+		if (!WARN(i915.verbose_state_checks, format))		\
 			DRM_ERROR(format);				\
-	}								\
 	unlikely(__ret_warn_on);					\
 })
 
 #define I915_STATE_WARN_ON(condition) ({				\
 	int __ret_warn_on = !!(condition);				\
-	if (unlikely(__ret_warn_on)) {					\
-		if (i915.verbose_state_checks)				\
-			WARN(1, "WARN_ON(" #condition ")\n");		\
-		else 							\
+	if (unlikely(__ret_warn_on))					\
+		if (!WARN(i915.verbose_state_checks,			\
+			  "WARN_ON(" #condition ")\n"))			\
 			DRM_ERROR("WARN_ON(" #condition ")\n");		\
-	}								\
 	unlikely(__ret_warn_on);					\
 })