Rename Cp2102SerialDriver to Cp21xxSerialDriver and add Usb IDs for more Silabs devices

Conflicts:
	UsbSerialLibrary/src/com/hoho/android/usbserial/driver/Cp21xxSerialDriver.java
	UsbSerialLibrary/src/com/hoho/android/usbserial/driver/UsbId.java
	UsbSerialLibrary/src/com/hoho/android/usbserial/driver/UsbSerialProber.java