ipv6: take care of disable_policy when restoring routes

ipv6: take care of disable_policy when restoring routes

When routes corresponding to addresses are restored by
fixup_permanent_addr(), the dst_nopolicy parameter was not set.
The typical use case is a user that configures an address on a down
interface and then put this interface up.

Let's take care of this flag in addrconf_f6i_alloc(), so that every callers
benefit ont it.

CC: stable@kernel.org
CC: David Forster <dforster@brocade.com>
Fixes: df789fe75206 ("ipv6: Provide ipv6 version of "disable_policy" sysctl")
Reported-by: Siwar Zitouni <siwar.zitouni@6wind.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20220623120015.32640-1-nicolas.dichtel@6wind.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>