davinci: Initial support for Omapl138-Hawkboard

This patch adds initial support for the Hawkboard-L138 system
It is under the machine name "omapl138_hawkboard".
This system is based on the da850 davinci CPU architecture.
Information on these system may be found at http://www.hawkboard.org.
Basic support for the UART console is included in this patch.
It's tested with latest Angstrom File Systems like ramdisk
from http://alturl.com/imb45.

Signed-off-by: Victor Rodriguez <victor.rodriguez@sasken.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>