net: tcp: send_syn_segment: Log packet before it's sent

After successful send, the packet is automatically cleared, so
trying to call print_send_info() on it leads to errors:

[net/pkt] [ERR] net_pkt_tcp_data: NULL fragment data!
[net/tcp] [ERR] net_tcp_get_hdr: NULL TCP header!

(if error logging enabled).

This change is similar to how print_send_info() is called in
existing send_reset() function of this source file.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>