tests: net: socket: Avoid macro error with zsock_sendto

The preprocessor gives this error when calling zsock_sendto
in user mode when there is a mismatch with amount of parameters
to the sendto wrapper call.

  tests/net/socket/udp/src/main.c: In function ‘comm_sendto_recvfrom’:
  tests/net/socket/udp/src/main.c:125:46: error: macro "zsock_sendto" \
                                 requires 6 arguments, but only 5 given
  125 |                             0, &addr, addrlen);
      |                                              ^
  In file included from include/zephyr/net/socket.h:1381,
                 from tests/net/socket/udp/src/main.c:15:
  include/generated/zephyr/syscalls/socket.h:266: note: \
                      macro "zsock_sendto" defined here
  266 | #define zsock_sendto(sock, buf, len, flags, dest_addr, addrlen)

Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>