mount: add support of devtmpfs

It's global, so it doesn't require any actions, they should be only mounted.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

mount.c

@@ -183,6 +183,7 @@ static char *fstypes[] = {
 	"unsupported",
 	"proc",
 	"sysfs",
+	"devtmpfs",
 };
 
 static u32 encode_fstype(char *fst)