Add a useful command to the Makefile

Since we say do to it on the web page, put it in the makefile
Signed-off-by: root <root@localhost.localdomain>

Change-Id: I38f0a177510ba829dfdddad7cfaca02b4beeec18
Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>
Reviewed-on: http://nxm.coreboot.org/review/74
Tested-by: Jenkins QA
Reviewed-by: John Floren <john@jfloren.net>

Makefile

@@ -1,4 +1,5 @@
 gitconfig:
 	for hook in commit-msg ; do if ! [ -x .git/hooks/$$hook ]; then cp util/gitconfig/$$hook .git/hooks/$$hook; chmod +x .git/hooks/$$hook; fi; done
 	git config remote.origin.push HEAD:refs/for/master
+	git config branch.autosetupmerge always
 	echo "Don't forget to set up your name and email in git"