Add support for TechNexion TAO3530 SoM

This patch has been posted quite a long time ago. I ported it to
the latest mainline U-Boot version. With some additional cleanup
and enhancements.
Signed-off-by: NTapani Utriainen <tapani@technexion.com>
CC: Sandeep Paulraj <s-paulraj@ti.com>
Signed-off-by: NStefan Roese <sr@denx.de>
Cc: Thorsten Eisbein <thorsten.eisbein@head-acoustics.de>
Cc: Tom Rini <trini@ti.com>