Add gerrit settings

Make it simple to setup and use this repo with 'git review' command.

Change-Id: I6bbe65cc09e086685995f084a07a646a7d60b93c
diff --git a/.gitreview b/.gitreview
new file mode 100644
index 0000000..4521e98
--- /dev/null
+++ b/.gitreview
@@ -0,0 +1,3 @@
+[gerrit]
+host=gerrit.osmocom.org
+project=osmo-trx