md: mark some personalities as deprecated

Mark the three personalities (linear, fault and multipath) as deprecated
because:

1. people can use dm multipath or nvme multipath.
2. linear is already deprecated in MODULE_ALIAS.
3. no one actively using fault.

Signed-off-by: Guoqing Jiang <jiangguoqing@kylinos.cn>
Signed-off-by: Song Liu <song@kernel.org>