comgt: support ZTE MF286R modem

comgt: support ZTE MF286R modem

The modem is based on Marvell PXA1826 and uses ACM+RNDIS interface to
establish connection with custom commands specific to ZTE modems.
Two variants of modems were discovered, some identifying themselves
as "ZTE", and others as plain "Marvell", the chipset manufacturer.
The modem itself runs a fork of OpenWrt inside, which root shell can be
accessed via ADB interface.

Signed-off-by: Cezary Jackiewicz <cezary@eko.one.pl>
Signed-off-by: Lech Perczak <lech.perczak@gmail.com>
(cherry picked from commit e02fb42c53bad5dd36726c6ef5a46bfe31d2e400)