add .gitreview

This adds a .gitreview file for use with the git-review tool. More
information is available at the URL below:
https://labsconsole.wikimedia.org/wiki/Git-review

Change-Id: I723d78bf7dd81c5756e684d5b166210246fe2daf
Signed-off-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: http://review.coreboot.org/1665
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

.gitreview

@@ -0,0 +1,5 @@
+[gerrit]
+host=review.coreboot.org
+port=29418
+project=coreboot
+defaultbranch=master