reiserfs: Fix memory leak in reiserfs_parse_options()

[ Upstream commit e9d4709fcc26353df12070566970f080e651f0c9 ]

When a usrjquota or grpjquota mount option is used multiple times, we
will leak memory allocated for the file name. Make sure the last setting
is used and all the previous ones are properly freed.

Reported-by:  <syzbot+c9e294bbe0333a6b7640@syzkaller.appspotmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>