So that the root filesystem can be fsck'd properly, mount it read only. Either
initscripts or systemd will re-mount as read-write in early boot.
(From OE-Core rev: 1ace2bdd8d6d950038fb6d9b83f6eceba276f588)
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>