project: enable battery voltage checking

Enable battery voltage checking before flashing or erasing
image.

Change-Id: Ie95f3b88d20b19cea711f9cef980590ceed0ff89
diff --git a/project/msm8952.mk b/project/msm8952.mk
index 6a06c96..f6d69b4 100644
--- a/project/msm8952.mk
+++ b/project/msm8952.mk
@@ -89,3 +89,6 @@
 CFLAGS += -Werror
 
 DEFINES += USE_TARGET_HS200_DELAY=1
+
+#enable battery voltage check
+DEFINES += CHECK_BAT_VOLTAGE=1