Kernel/USB: Use "Pipe" instead of "USBPipe" in USBEndpoint

This wasn't caught before because nothing was including this header.

Kernel/Bus/USB/USBEndpoint.h

@@ -56,7 +56,7 @@ private:
     USBEndpoint(/* TODO */);
     USBEndpointDescriptor m_descriptor;
 
-    USBPipe m_pipe;
+    Pipe m_pipe;
 };
 
 }