netfilter: iptable_raw: drop bogus net_init annotation

This is a leftover from the times when this function was wired up via
pernet_operations.  Now its called when userspace asks for the table.

With CONFIG_NET_NS=n, iptable_raw_table_init memory has been discarded
already and we get a kernel crash.

Other tables are fine, __net_init annotation was removed already.

Fixes: fdacd57c ("netfilter: x_tables: never register tables by default")
Reported-by: youling 257 <youling257@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>