[ARM] pxa: add U2D registers and bits definitions

This should be eventually moved to somewhere closer to the U2D driver,
but is kept here atm so it's easier for USB configuration code to work.

Signed-off-by: Igor Grinberg <grinberg@compulab.co.il>
Signed-off-by: Mike Rapoport <mike@compulab.co.il>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>