test: af_packet: Do not change proto to network order when creating socket

The setup_socket() function calls socket() with proto changed to network
order. In this case functions with zsock_* prefix are called instead of
zpacket_*. The problem is with 'packet_is_supported()' method from
sockets_packet.c, which returns false when ETH_P_ALL proto is converted
with htons().

This patch fixes this issue by removing the htons() call.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
Suggested-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>