subsys: usb: Fixes USB DFU class by updating the bcdUSB value.

bcdUSB has been previously updated from 1.1 to 2.0 in default
device descriptor, but not in DFU class. After USB bus reset
performed by dfu-util, alternative descriptor is registered
with bcdUSB set to 1.1. This mismatch causes communication failure.
DFU descriptor's bcdUSB has been updated to match default one.

Relates to #7570

Signed-off-by: Paweł Zadrożniak <pawel.zadrozniak@nordicsemi.no>

subsys/usb/class/usb_dfu.c

@@ -114,7 +114,7 @@ struct dev_dfu_mode_descriptor dfu_mode_desc = {
 	.device_descriptor = {
 		.bLength = sizeof(struct usb_device_descriptor),
 		.bDescriptorType = USB_DEVICE_DESC,
-		.bcdUSB = sys_cpu_to_le16(USB_1_1),
+		.bcdUSB = sys_cpu_to_le16(USB_2_0),
 		.bDeviceClass = 0,
 		.bDeviceSubClass = 0,
 		.bDeviceProtocol = 0,