ipv4: raw: move struct raw_sock and raw_sk() to include/net/raw.h

A following patch will use struct raw_sock to store state for ipmr,
so having the definitions in icmp.h doesn't fit very well anymore.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>