fix mkfs.ext4 parameters

introduced in 70595df7ba

setup.sh

@@ -25,12 +25,12 @@ unset root_pwd
 chroot=/mnt/root-unlocked
 
 # root device
-mkfs.ext4 -f /dev/mapper/root-unlocked
+mkfs.ext4 /dev/mapper/root-unlocked
 mkdir /mnt/root-unlocked
 mount /dev/mapper/root-unlocked /mnt/root-unlocked
 
 # boot device
-mkfs.ext4 -f "$boot"
+mkfs.ext4 "$boot"
 mkdir "$chroot/boot"
 mount "$boot" "$chroot/boot"