omap2: add USB initialization for tusb6010

Based on Kalle's and Tony's patches. Some variables re-organized
and unused code removed.

Signed-off-by: Kalle Valo <kalle.valo@iki.fi>
Signed-off-by: Francisco Alecrim <francisco.alecrim@openbossa.org>
[tony@atomide.com: this is needed to fix the related tusb6010 DMA API changes]
Signed-off-by: Tony Lindgren <tony@atomide.com>