board: ti: am43xx: add support for AM43xx Industrial Development Kit

AM43xx Industrial Development Kit is a new board
based on AM437x line of SoCs. Targetted at Industrial
Automation applications, it comes with EtherCAT, motor
control and other goodies.

Thanks to James Doublesin for all the help.

Cc: James Doublesin <doublesin@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>