update-makefiles-helper.sh for vendor folders

Now update-makefiles-helper.sh also works for vendor folders.

Bug: 38216114
Test: ./hardware/interfaces/update-makefiles.sh works, generated
Android.bp files are identical w/wo this change.
/vendor/xxx/hardware/interfaces/update-makefiles.sh also works.

Change-Id: I85d5f0178a9147dac7034a74ec4bb5438267476f
diff --git a/update-makefiles-helper.sh b/update-makefiles-helper.sh
index 5e6284f..0460a41 100755
--- a/update-makefiles-helper.sh
+++ b/update-makefiles-helper.sh
@@ -54,10 +54,10 @@
 #
 # Usage: get_bp_dirs dir
 function get_bp_dirs() {
-  find $1/*/                         \
+  find $1/*                          \
+    -mindepth 1                      \
     -name "Android.bp"               \
-    -printf "%h\n"                   \
-    | cut -d "/" -f1-3               \
+    -printf "%H\n"                   \
     | sort | uniq
 }