btrfs-progs: mkfs make --uuid require an argument

$ mkfs.btrfs --uuid 1234... /dev/sdx
Error: error checking 1234...  status: No such file or directory

Signed-off-by: David Sterba <dsterba@suse.cz>

mkfs.c

@@ -352,7 +352,7 @@ static struct option long_options[] = {
 	{ "rootdir", 1, NULL, 'r' },
 	{ "nodiscard", 0, NULL, 'K' },
 	{ "features", 1, NULL, 'O' },
-	{ "uuid", 0, NULL, 'U' },
+	{ "uuid", required_argument, NULL, 'U' },
 	{ NULL, 0, NULL, 0}
 };