correct branch id to 'IF'

Change-Id: I7fd338f355511869559cc5b407b82e77dc3425ed
diff --git a/core/build_id.mk b/core/build_id.mk
index 1bf67c0..5751d73 100644
--- a/core/build_id.mk
+++ b/core/build_id.mk
@@ -18,4 +18,4 @@
 # # (like "CRB01").  It must be a single word, and is
 # # capitalized by convention.
 #
-export BUILD_ID=IPK77
+export BUILD_ID=IFK77