Makefile: add dirty tag if git repo was modified.

Currently any uncommitted changes are not displayed properly.
example a "dirty git repo" will still show v1.69 as the version.

To differentiate, we should rather add --dirty option to git describe
to display the delta.

Signed-off-by: Nishanth Menon <nm@ti.com>

Makefile

@@ -349,7 +349,7 @@ builddate.c:	$(ALLOBJECTS)
 		echo 'char *builddate="'`date`'";' > builddate.c
 
 version.c:	$(ALLOBJECTS)
-		echo 'char *omapconf_version="'`git describe||echo "$(VERSION_MAJOR).$(VERSION_MINOR)-nogit"`'";' > version.c
+		echo 'char *omapconf_version="'`git describe --dirty||echo "$(VERSION_MAJOR).$(VERSION_MINOR)-nogit"`'";' > version.c