get rid of open-coded S_ISREG(), etc.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 8878370..4def4d9 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1740,7 +1740,7 @@
 {
 	u32 av = 0;
 
-	if ((mode & S_IFMT) != S_IFDIR) {
+	if (!S_ISDIR(mode)) {
 		if (mask & MAY_EXEC)
 			av |= FILE__EXECUTE;
 		if (mask & MAY_READ)