samples: shell_module: use generic CDC ACM shield

Remove CDC ACM UART devicetree and config overlay, and explicit
USB support initialization in favor of generic CDC ACM shield.
For shell support via USB CDC ACM, this example is to be built
as follows:

west build -b nrf52840dongle_nrf52840
  samples/subsys/shell/shell_module -- -DSHIELD=cdc_acm_shell

Signed-off-by: Johann Fischer <[email protected]>

Author: jfischer-no

samples/subsys/shell/shell_module/overlay-usb.conf

@@ -14,8 +14,7 @@ tests:
     tags: shell usb
     harness: keyboard
     min_ram: 40
-    extra_args: OVERLAY_CONFIG="overlay-usb.conf"
-                DTC_OVERLAY_FILE="usb.overlay"
+    extra_args: SHIELD="cdc_acm_shell"
   sample.shell.shell_module.minimal:
     filter: CONFIG_SERIAL and dt_chosen_enabled("zephyr,shell-uart")
     tags: shell

samples/subsys/shell/shell_module/sample.yaml

@@ -344,19 +344,4 @@ void main(void)
 	if (IS_ENABLED(CONFIG_SHELL_START_OBSCURED)) {
 		login_init();
 	}
-
-#if DT_NODE_HAS_COMPAT(DT_CHOSEN(zephyr_shell_uart), zephyr_cdc_acm_uart)
-	const struct device *dev;
-	uint32_t dtr = 0;
-
-	dev = DEVICE_DT_GET(DT_CHOSEN(zephyr_shell_uart));
-	if (!device_is_ready(dev) || usb_enable(NULL)) {
-		return;
-	}
-
-	while (!dtr) {
-		uart_line_ctrl_get(dev, UART_LINE_CTRL_DTR, &dtr);
-		k_sleep(K_MSEC(100));
-	}
-#endif
 }