Update the USB serial option driver to support MeiG Smart SLM320.

ID 2dee:4d41 UNISOC UNISOC-8910

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=2dee ProdID=4d41 Rev=00.00
S: Manufacturer=UNISOC
S: Product=UNISOC-8910
C: #Ifs= 8 Cfg#= 1 Atr=e0 MxPwr=400mA
I: If#= 0 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=00 Prot=00 Driver=option
E: Ad=01(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I: If#= 1 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=00 Prot=00 Driver=option
E: Ad=02(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=82(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I: If#= 2 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=00 Prot=00 Driver=option
E: Ad=03(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=83(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I: If#= 3 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=00 Prot=00 Driver=option
E: Ad=04(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I: If#= 4 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=00 Prot=00 Driver=option
E: Ad=05(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=85(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I: If#= 5 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=00 Prot=00 Driver=option
E: Ad=06(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=86(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I: If#= 6 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=00 Prot=00 Driver=option
E: Ad=07(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=87(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I: If#= 7 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=00 Prot=00 Driver=option
E: Ad=08(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=88(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms

Tested successfully a PPP LTE connection using If#= 0.
Not sure of the purpose of every other serial interfaces.
Signed-off-by: Aurélien Jacobs <aurel@gnuage.org>
Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>