f2fs/012: adapt lookup_mode=x mount option

f2fs/012: adapt lookup_mode=x mount option

w/ below change [1], f2fs will enable lookup_mode=perf by default, it
will change f2fs dirent lookup method from linear based lookup to hash
based lookup.

So that, f2fs will ignore sb.s_encoding_flags by default, which is not
compatible w/ f2fs/012 testcase, in where it will control lookup method
by configuring this flag w/ fsck.f2fs.

To avoid failure of f2fs/012, let's check whether f2fs has supported
"lookup_mode=auto" mount option, mount w/ the option if it can,
otherwise, don't.

[1] https://lore.kernel.org/linux-f2fs-devel/20250805065228.1473089-1-chullee@google.com

Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Daniel Lee <chullee@google.com>
Signed-off-by: Chao Yu <chao@kernel.org>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>