ext4: make ext4_show_options() be table-driven

Consistently show mount options which are the non-default, so that
/proc/mounts accurately shows the mount options that would be
necessary to mount the file system in its current mode of operation.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --cc fs/ext4/ext4.h
Simple merge

diff --cc fs/ext4/super.c
Simple merge