Fix build when TW_MAX_BRIGHTNESS is not set

Fixes regression introduced with max_brightness fix patch

Change-Id: I5e9d1164cdf78311cec8326d0e09efd428c011a8
diff --git a/Android.mk b/Android.mk
index 87f92fc..1d45095 100644
--- a/Android.mk
+++ b/Android.mk
@@ -383,8 +383,8 @@
 ifneq ($(TW_MAX_BRIGHTNESS),)
 	LOCAL_CFLAGS += -DTW_MAX_BRIGHTNESS=$(TW_MAX_BRIGHTNESS)
 else
-    ifeq ($(filter $(TW_NO_SCREEN_BLANK) $(TW_BRIGHTNESS_PATH),),)
-        $(call pretty-error,TW_MAX_BRIGHTNESS must be defined if using TW_NO_SCREEN_BLANK or TW_BRIGHTNESS_PATH. Please update your device tree to include this flag with the correct value from your device.)
+    ifneq ($(TW_NO_SCREEN_BLANK),)
+        $(call pretty-error,TW_MAX_BRIGHTNESS must be defined if using TW_NO_SCREEN_BLANK. Please update your device tree to include this flag with the correct value from your device.)
     endif
 endif
 ifneq ($(TW_DEFAULT_BRIGHTNESS),)