selinux: fix sel_write_enforce broken return value

Return a negative error value like the rest of the entries in this function.

Cc: <stable@vger.kernel.org>
Signed-off-by: Joe Perches <joe@perches.com>
Acked-by:  Stephen Smalley <sds@tycho.nsa.gov>
[PM: tweaked subject line]
Signed-off-by: Paul Moore <pmoore@redhat.com>
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 33db1ad..138949a 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -152,7 +152,7 @@
 		goto out;
 
 	/* No partial writes. */
-	length = EINVAL;
+	length = -EINVAL;
 	if (*ppos != 0)
 		goto out;