Fix incorrect control P/F encoding in src/sock.c wherein the P/F flag
value was passed to patty_ax25_sock_send() as an information field body
length, rather than the pf argument for the internal functions
control_i(), control_s(), and control_u(); this corrects the following
functions:
* patty_ax25_sock_send_rr()
* patty_ax25_sock_send_rnr()
* patty_ax25_sock_send_rej()