tests: modem: cmux: add missing timeout param

Add the missing timeout parameter to `modem_pipe_open()` and
`modem_pipe_close()` calls.
10 seconds is the default value used in the Zephyr tree.

Fixes a regression introduced in
zephyrproject-rtos/zephyr#74325.

Signed-off-by: Tomi Fontanilles <tomi.fontanilles@nordicsemi.no>

tests/subsys/modem/modem_cmux/src/main.c

@@ -793,14 +793,14 @@ ZTEST(modem_cmux, test_modem_cmux_prevent_work_while_released)
 	/* Validate no new requests can be submitted */
 	modem_cmux_connect(&cmux);
 	modem_cmux_disconnect(&cmux);
-	modem_pipe_open(dlci1_pipe);
-	modem_pipe_open(dlci2_pipe);
+	modem_pipe_open(dlci1_pipe, K_SECONDS(10));
+	modem_pipe_open(dlci2_pipe, K_SECONDS(10));
 	modem_pipe_transmit(dlci1_pipe, transmit, sizeof(transmit));
 	modem_pipe_transmit(dlci2_pipe, transmit, sizeof(transmit));
 	modem_pipe_receive(dlci1_pipe, receive, sizeof(receive));
 	modem_pipe_receive(dlci2_pipe, receive, sizeof(receive));
-	modem_pipe_close(dlci1_pipe);
-	modem_pipe_close(dlci2_pipe);
+	modem_pipe_close(dlci1_pipe, K_SECONDS(10));
+	modem_pipe_close(dlci2_pipe, K_SECONDS(10));
 	k_msleep(500);
 	zassert_true(modem_backend_mock_get(&bus_mock, buffer1, sizeof(buffer1)) == 0);
 
@@ -809,9 +809,9 @@ ZTEST(modem_cmux, test_modem_cmux_prevent_work_while_released)
 	modem_backend_mock_prime(&bus_mock, &transaction_control_sabm);
 	zassert_ok(modem_cmux_connect(&cmux));
 	modem_backend_mock_prime(&bus_mock, &transaction_dlci1_sabm);
-	zassert_ok(modem_pipe_open(dlci1_pipe));
+	zassert_ok(modem_pipe_open(dlci1_pipe, K_SECONDS(10)));
 	modem_backend_mock_prime(&bus_mock, &transaction_dlci2_sabm);
-	zassert_ok(modem_pipe_open(dlci2_pipe));
+	zassert_ok(modem_pipe_open(dlci2_pipe, K_SECONDS(10)));
 }
 
 ZTEST_SUITE(modem_cmux, NULL, test_modem_cmux_setup, test_modem_cmux_before, NULL, NULL);