ARM: da850evm: Remove legacy OHCI referencs and unify platform

OHCI was added with DM_USB support, so there are a few unneeded
items in the header file that can be removed.  This also
unifies da850evm with NOR and NAND booting options so all have
OHCI support.

Signed-off-by: Adam Ford <aford173@gmail.com>
[trini: Migrate da850_am18xxevm]
Signed-off-by: Tom Rini <trini@konsulko.com>