omap3_beagle: Finish current outstanding DM migrations

At this point in time we can now remove our legacy code and switch to
enabling DM for USB and Ethernet.

Cc: Derald D. Woods <woods.technical@gmail.com>
Cc: Adam Ford <aford173@gmail.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
Tested-by: Derald D. Woods <woods.technical@gmail.com>