When converting directory from in-ICB to normal format, the last
iteration through the directory fixing up directory enteries can fail
due to ENOMEM. We do not expect this iteration to fail since the
directory is already verified to be correct and it is difficult to undo
the conversion at this point. So just use GFP_NOFAIL to make sure the
small allocation cannot fail.

Reported-by: syzbot+111eaa994ff74f8d440f@syzkaller.appspotmail.com
Fixes: 0aba4860 ("udf: Allocate name buffer in directory iterator on heap")
Signed-off-by: Jan Kara <jack@suse.cz>