Add support for NEXIO (or iNexio) USB touchscreens to usbtouchscreen
driver.  Tested with NEX170MRT 17" LCD monitor with integrated touchscreen
(with xserver-xorg-input-evtouch 0.8.8-1):

T:  Bus=02 Lev=01 Prnt=01 Port=01 Cnt=01 Dev#= 54 Spd=12  MxCh= 0
D:  Ver= 1.10 Cls=02(comm.) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
P:  Vendor=1870 ProdID=0001 Rev= 1.00
S:  Manufacturer=iNexio
S:  Product=iNexio USB
C:* #Ifs= 2 Cfg#= 1 Atr=c0 MxPwr=500mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=02(comm.) Sub=02 Prot=00 Driver=(none)
E:  Ad=83(I) Atr=03(Int.) MxPS=   8 Ivl=255ms
I:* If#= 1 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=(none)
E:  Ad=01(O) Atr=02(Bulk) MxPS=  64 Ivl=0ms
E:  Ad=82(I) Atr=02(Bulk) MxPS=  64 Ivl=0ms

No datasheet is available, this was written by capturing some data with
SniffUSB in Windows: http://www.rainbow-software.org/linux_files/nexio/Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>