[NETLINK]: w1_int.c: fix default netlink group

w1 does not need to multicast its state to several groups at once,
and upcoming netlink changes will not allow bitmask for groups anyway.

Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>