ext4: fix i_version handling on remount

i_version mount option is getting lost on remount. This is because the
'i_version' mount option differs from the util-linux mount option
'iversion', but it has exactly the same functionality. We have to
specifically notify the vfs that this is what we want by setting
appropriate flag in fc->sb_flags. Fix it and as a result we can remove
*flags argument from __ext4_remount(); do the same for
__ext4_fill_super().

In addition set out to deprecate ext4 specific 'i_version' mount option
in favor or 'iversion' by kernel version 5.20.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Fixes: cebe85d5

 ("ext4: switch to the new mount api")
Link: https://lore.kernel.org/r/20211222104517.11187-2-lczerner@redhat.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>