AndroidBoot: Flag to distinguish VB key used

Add new flag to decide the type of key used
for setting ROT during OTA test cases.

Change-Id: I9c970be3e1fec0709cfd8226c2679298dcce0bdf
diff --git a/makefile b/makefile
index 9822cc5..9e9e861 100644
--- a/makefile
+++ b/makefile
@@ -127,6 +127,10 @@
   DEFINES += _SIGNED_KERNEL=1
 endif
 
+ifeq ($(VB1_KEY_USED),1)
+  DEFINES += VB1_KEY_USED=1
+endif
+
 ifeq ($(DYNAMIC_PARTITION_SUPPORT),1)
   DEFINES += DYNAMIC_PARTITION_SUPPORT=1
 endif