update doc

Signed-off-by: Nshawn_he <shawn.he@huawei.com>

en/application-dev/device/usb-guidelines.md

 # USB Service Development
 
+The USB service provides the following functions: query of USB device list, bulk data transfer, control transfer, and access permission management.
+
 ## When to Use
 
 In Host mode, you can obtain the list of connected devices, enable or disable the devices, manage device access permissions, and perform data transfer or control transfer.
 
 ## APIs
 
-The USB service provides the following functions: query of USB device list, bulk data transfer, control transfer, and access permission management.
-
 The following table lists the USB APIs currently available. For details, see the [API Reference](../reference/apis/js-apis-usb.md).
 
 **Table  1**  Open USB APIs