macvlan: disable SIOCSHWTSTAMP in container

Miroslav pointed that with NET_ADMIN enabled in container, a normal user
could be mapped to root and is able to change the real device's rx
filter via ioctl on macvlan, which would affect the other ptp process on
host. Fix it by disabling SIOCSHWTSTAMP in container.

Fixes: 254c0a2b ("macvlan: pass get_ts_info and SIOC[SG]HWTSTAMP ioctl to real device")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>