Add SystemUI.apk to the generic build.

Change-Id: I03d92d93fbcb51808a096fb7d48c1b693efa777d
diff --git a/target/product/generic.mk b/target/product/generic.mk
index f05c441..1f26a75 100644
--- a/target/product/generic.mk
+++ b/target/product/generic.mk
@@ -39,6 +39,7 @@
     QuickSearchBox \
     Settings \
     Sync \
+    SystemUI \
     Updater \
     CalendarProvider \
     SyncProvider