EP_ATLAS: Remove requirement for USB library if not required

Move inclusion of USB header file within the existing
conditional pre-processor directive so the USB library
is not required if USB stdio console is disable

Author: hugueskamba

targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/TARGET_MCU_NRF52840/TARGET_EP_ATLAS/usb_stdio.cpp

@@ -16,15 +16,15 @@
  * limitations under the License.
  */
 
-#include "USBSerial.h"
-#include "platform/mbed_retarget.h"
-
 #ifndef MBED_CONF_EP_ATLAS_ENABLE_USB_STDIO_CONSOLE
 #define MBED_CONF_EP_ATLAS_ENABLE_USB_STDIO_CONSOLE 0
 #endif
 
 #if MBED_CONF_EP_ATLAS_ENABLE_USB_STDIO_CONSOLE
 
+#include "USBSerial.h"
+#include "platform/mbed_retarget.h"
+
 /* Retarget stdio to USBSerial */
 mbed::FileHandle *mbed::mbed_target_override_console(int fd)
 {