fix syntax error in travis file

.travis.yml

@@ -1,9 +1,12 @@
 language: c
-notifications:                                                                                                          email:                                                                                                                   recipients:                                                                                                              - wbx@openadk.org
-       on_success: always
-       on_failure: always
+notifications:
+  email:
+    recipients:
+      - wbx@openadk.org
+    on_success: always
+    on_failure: always
 git:
-  depth: 3
+  depth: 2
 matrix:
   include:
   - env: ARCH=arm SYSTEM=beaglebone-black