tools: add checkpatch script

execute from openocd root dir after commiting change but before
pushing to gerrit.
tools/checkpatch.sh

This is the same script used by the jenkins build server to validate
a change.

Change-Id: Ib40d44b160e1c50a5e47ab55fc48a554381ea763
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/167
Tested-by: jenkins

tools/checkpatch.sh

@@ -0,0 +1,4 @@
+#!/bin/sh
+#
+
+git format-patch -M --stdout HEAD^ | tools/scripts/checkpatch.pl - --no-tree