Rename SELinux source files

The name rc-selinux-util.* is a bit long, so I renamed the source files
to rc-selinux.*

X-Gentoo-Bug: 516956
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=516956

src/rc/checkpath.c

@@ -47,7 +47,7 @@
 #include "rc-misc.h"
 
 #ifdef HAVE_SELINUX
-#include "rc-selinux-util.h"
+#include "rc-selinux.h"
 #endif
 
 typedef enum {