docs: add gerrit server url

Change-Id: If39b522594a4ee3758fb85309af01f7a98c9f939
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/553
Tested-by: jenkins

HACKING

@@ -154,6 +154,9 @@ master branch will be much reduced.
 
 If a contributor pushes a patch, it is considered good form if another
 contributor actually approves and submits that patch.
+
+@section browsing Browsing Patches
+All OpenOCD patches can be reviewed <a href="http://openocd.zylin.com/">here</a>.
 */
 /** @file
 This file contains the @ref patchguide page.