xfs: eliminate lockdep false positives in xfs_attr_shortform_list

xfs_attr_shortform_list() only called from a non-transactional context, it
hold ilock before alloc memory and maybe trapped in memory reclaim. Since
commit 204fae32("xfs: clean up remaining GFP_NOFS users") removed
GFP_NOFS flag, lockdep warning will be report as [1]. Eliminate lockdep
false positives by use __GFP_NOLOCKDEP to alloc memory
in xfs_attr_shortform_list().

[1] https://lore.kernel.org/linux-xfs/000000000000e33add0616358204@google.com/



Reported-by:  <syzbot+4248e91deb3db78358a2@syzkaller.appspotmail.com>
Signed-off-by: Long Li <leo.lilong@huawei.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>