linux-user: handle AF_PACKET sockaddrs in target_to_host_sockaddr

Implement conversion of the AF_PACKET sockaddr subtype
in target_to_host_sockaddr.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>