modem: fix socket descriptor leak

z_free_fd() is called twice then you close(). For example in ublox sara
r4 driver offload_close() calls modem_socket_put() where z_free_fd() is
called first time. Then this same function is called another time in
socket.c in z_impl_zsock_close() after this function has called
offload_close() in ublox sara r4 driver. This causes socket
descriptor leak.

Fixes #26819

Signed-off-by: Akseli Peltola <[email protected]>

drivers/modem/modem_socket.c

@@ -233,7 +233,6 @@ void modem_socket_put(struct modem_socket_config *cfg, int sock_fd)
 
 	k_sem_take(&cfg->sem_lock, K_FOREVER);
 
-	z_free_fd(sock->sock_fd);
 	sock->id = cfg->base_socket_num - 1;
 	sock->sock_fd = -1;
 	sock->is_waiting = false;