fix issue nrf52840 not reset properly when upgrading bootloader+sd combo

- root cause tusb_task()/cdc task is called when usb is not inited (in
case of sd upgrade)

Author: hathach

Makefile

@@ -28,7 +28,7 @@ SD_HEX       = $(SD_PATH)/$(SD_FILENAME)_softdevice.hex
 LD_FILE      = $(SRC_PATH)/linker/$(SD_NAME)_v$(SD_VER1).ld
 
 MERGED_FNAME = $(OUTPUT_FILENAME)_$(SD_NAME)_$(SD_VERSION)
-RELEASE_DIR  = bin/$(BOARD)/$(SD_VERSION)
+RELEASE_DIR  = bin/$(BOARD)
 
 
 MK_DIS_FIRMWARE = "$(SD_NAME) $(SD_VERSION)"

lib/sdk11/components/libraries/bootloader_dfu/bootloader.c

@@ -128,8 +128,9 @@ static void wait_for_events(void)
     app_sched_execute();
 
 #ifdef NRF52840_XXAA
-    // usb is not enabled in OTA
-    if ( !is_ota() )
+    // skip if usb is not inited ( e.g OTA / finializing sd/bootloader )
+    extern bool usb_inited(void);
+    if ( usb_inited() )
     {
       tusb_task();
       tud_cdc_write_flush();

src/usb/usb.c

@@ -65,8 +65,20 @@ extern void tusb_hal_nrf_power_event(uint32_t event);
 
 
 //------------- IMPLEMENTATION -------------//
+static bool _inited = false;
+
+bool usb_inited(void)
+{
+  return _inited;
+}
+
 void usb_init(bool cdc_only)
 {
+  // skipped if already inited
+  if ( _inited ) return;
+
+  _inited = true;
+
   // USB power may already be ready at this time -> no event generated
   // We need to invoke the handler based on the status initially
   uint32_t usb_reg;