ext4: filesystems without casefold feature cannot be mounted with siphash

When mounting the ext4 filesystem, if the default hash version is set to
DX_HASH_SIPHASH but the casefold feature is not set, exit the mounting.

Reported-by:  <syzbot+340581ba9dceb7e06fb3@syzkaller.appspotmail.com>
Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
Link: https://patch.msgid.link/20240605012335.44086-1-lizhi.xu@windriver.com


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