config: am335x_evm: detect Black Wireless using BWA

config: am335x_evm: detect Black Wireless using BWA

BeagleBone Black Wireless is clone of the BeagleBone Black (BBB) with
the Ethernet replaced by a TI wl1835 wireless module.

This board can be indentified by the BWAx value after A335BNLT (BBB)
in the at24 eeprom:
BWAx [aa 55 33 ee 41 33 33 35  42 4e 4c 54 42 57 41 35  |.U3.A335BNLTBWA5|]

http://beagleboard.org/black-wireless
https://github.com/beagleboard/beaglebone-black-wireless

firmware: https://github.com/beagleboard/beaglebone-black-wireless/tree/master/firmware
wl18xx mac address: /proc/device-tree/ocp/ethernet@4a100000/slave@4a100200/mac-address

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>