arm, davinci: add support for am1808 based enbw_cmc board

- booting from NOR Flash with direct boot method
- POST support
- LOGBUF support

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Paulraj Sandeep <s-paulraj@ti.com>
Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
Cc: Igor Grinberg <grinberg@compulab.co.il>
Cc: Christian Riesch <christian.riesch@omicron.at>