USB: serial: option: Add support for ZTE MF871A

This patch adds support for MF871A USB modem (aka Speed USB STICK U03)
to option driver. This modem is manufactured by ZTE corporation, and
sold by KDDI.

Interface layout:
0: AT
1: MODEM

usb-devices output:
T:  Bus=01 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#=  9 Spd=480 MxCh= 0
D:  Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=19d2 ProdID=1481 Rev=52.87
S:  Manufacturer=ZTE,Incorporated
S:  Product=ZTE Technologies MSM
S:  SerialNumber=1234567890ABCDEF
C:  #Ifs= 2 Cfg#= 1 Atr=80 MxPwr=500mA
I:  If#= 0 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=00 Driver=option
I:  If#= 1 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=00 Driver=option

Co-developed-by: Hiroyuki Yamamoto <hyamamo@allied-telesis.co.jp>
Signed-off-by: Hiroyuki Yamamoto <hyamamo@allied-telesis.co.jp>
Signed-off-by: Yoshiaki Okamoto <yokamoto@allied-telesis.co.jp>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>