omni: fix PRODUCT_NO_CHARGER and make it TARGET_NO_CHARGER

not is not the same as not not

Change-Id: I70d4a0d811178c2fc27c74ade4f8efd88dbecc8a
diff --git a/charger/Android.mk b/charger/Android.mk
index 047a2d0..8011235 100644
--- a/charger/Android.mk
+++ b/charger/Android.mk
@@ -1,4 +1,4 @@
-ifeq ($(PRODUCT_NO_CHARGER),true)
+ifneq ($(TARGET_NO_CHARGER),true)
 LOCAL_PATH := $(call my-dir)
 
 ifneq (,$(PRODUCT_AAPT_PREF_CONFIG))