update docs

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

en/device-dev/subsystems/subsys-usbservice-overview.md

@@ -72,7 +72,7 @@
 </tr>
 <tr id="row18831119115815"><td class="cellrowborder" valign="top" headers="mcps1.2.4.1.1 "><p id="p48323975814"><a name="p48323975814"></a><a name="p48323975814"></a>int32_t ControlTransfer(USBDevicePipe &pip, const UsbCtrlTransfer &ctrl, std::vector<uint8_t> &vdata);</p>
 </td>
-<td class="cellrowborder" valign="top" headers="mcps1.2.4.1.2 "><p id="p15832129135813"><a name="p15832129135813"></a><a name="p15832129135813"></a>Performs control transfer for endpoint 0 of the device. The transmission direction is determined by the request type.</p>
+<td class="cellrowborder" valign="top" headers="mcps1.2.4.1.2 "><p id="p15832129135813"><a name="p15832129135813"></a><a name="p15832129135813"></a>Performs a control transfer for endpoint 0 of the device. The transmission direction is determined by the request type.</p>
 </td>
 </tr>
 <tr id="row71857914585"><td class="cellrowborder" valign="top" headers="mcps1.2.4.1.1 "><p id="p1318619155811"><a name="p1318619155811"></a><a name="p1318619155811"></a>int32_t SetConfiguration(USBDevicePipe &pip, const USBConfig &config);</p>