Use the correct PID

The VID:PID pair 1209:9DB5 is now officially assigned for the PD Buddy
Sink.  Thanks, Arachnid!  Now the firmware uses its proper PID instead
of the testing one.

src/usbcfg.c

             0x00,          /* bDeviceProtocol.                 */
             0x40,          /* bMaxPacketSize.                  */
             0x1209,        /* idVendor (pid.codes).            */
-            0x0001,        /* idProduct.                       */
+            0x9DB5,        /* idProduct (PD Buddy Sink).       */
             0x0200,        /* bcdDevice.                       */
             1,             /* iManufacturer.                   */
             2,             /* iProduct.                        */