build: adjust checkpatch for HEAD.

README is called README.md in git HEAD, and we have a directory
heal.

Change-Id: I2e698b95c6924b5b21aa54257fefd6a6698255ee
BUG: 1198849
Signed-off-by: Michael Scherer <misc@zarb.org>
Reviewed-on: http://review.gluster.org/9784
Reviewed-by: Humble Devassy Chirammal <humble.devassy@gmail.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Niels de Vos <ndevos@redhat.com>

extras/checkpatch.pl

@@ -614,13 +614,14 @@ sub top_of_glusterfs_tree {
         "glusterfsd",
         "glusterfs-hadoop",
         "glusterfs.spec.in",
+        "heal",
         "INSTALL",
         "libgfchangelog.pc.in",
         "libglusterfs",
         "MAINTAINERS",
         "Makefile.am",
         "NEWS",
-        "README",
+        "README.md",
         "rfc.sh",
         "rpc",
         "run-tests.sh",