config: Enable ext4 journaling by default.

Not having a journal by default is a major "gotcha".

Because openwrt does not fsck on boot, a power loss without journaling
can result in a dirty filesystem that openwrt will mount as read-only
which requires intervention to restore the router to working order.

Signed-off-by: Jordan Woyak <jordan.woyak@gmail.com>
(cherry picked from commit f9f2426e398cf74d1098ae40317bfba677ac7560)
Link: https://github.com/openwrt/openwrt/pull/15898


Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>