USB: cp210x: add MMB and PI ZigBee USB Device Support

Added support for MMB Networks and Planet Innovation Ingeni ZigBee USB
devices using customized Silicon Labs' CP210x.c USB to UART bridge
drivers with PIDs: 88A4, 88A5.

Signed-off-by: Sami Rahman <sami.rahman@mmbresearch.com>
Tested-by: Sami Rahman <sami.rahman@mmbresearch.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>