MAINTAINERS: update SELinux file patterns

Update MAINTAINERS to reflect that there are no SELinux headers under
include/linux, but we do have include/uapi/linux/selinux_netlink.h.
Reported-by: Joe Perches <joe@perches.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

MAINTAINERS

@@ -13937,7 +13937,7 @@ W:	https://selinuxproject.org
 W:	https://github.com/SELinuxProject
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux.git
 S:	Supported
-F:	include/linux/selinux*
+F:	include/uapi/linux/selinux_netlink.h
 F:	security/selinux/
 F:	scripts/selinux/
 F:	Documentation/admin-guide/LSM/SELinux.rst