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

commit 7681156982026ebf7eafd7301eb0374d7648d068 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>