config: am335x_evm: detect Green Wireless using GW1

config: am335x_evm: detect Green Wireless using GW1

SeeedStudio BeagleBone Green Wireless (BBGW) is an expansion of the
SeeedStudio Green (BBG) with the Ethernet replaced by a TI wl1835
wireless module.

This board can be indentified by the GW1x value after A335BNLT (BBB)
in the at24 eeprom:
GW1x [aa 55 33 ee 41 33 33 35  42 4e 4c 54 47 57 31 41  |.U3.A335BNLTGW1A|]

http://beagleboard.org/green-wireless
http://wiki.seeed.cc/BeagleBone_Green_Wireless/

firmware: https://github.com/beagleboard/beaglebone-black-wireless/tree/master/firmware
wl18xx mac address: Stored in at24 eeprom at address 5-16:
hexdump -e '8/1 "%c"' /sys/bus/i2c/devices/0-0050/eeprom | cut -b 5-16

Signed-off-by: Robert Nelson <robertcnelson@gmail.com>
CC: Tom Rini <trini@konsulko.com>
CC: Jason Kridner <jkridner@beagleboard.org>
CC: Will Newton <willn@resin.io>
Reviewed-by: Tom Rini <trini@konsulko.com>