dreamplug: initial board support.

Copied wholeheartedly from board/Marvell/guruplug and modified to add support
for SPI NOR flash.

CONFIG_MACH_DREAMPLUG defined in include/configs/dreamplug.h until Linus's
kernel.org tree adds it to mach-types.h.  Once it trickles down, the definition
can be removed from include/configs/dreamplug.h.

Signed-off-by: Jason Cooper <u-boot@lakedaemon.net>