staging: octeon-usb: Probe via device tree populated platform device.

Extract clocking parameters from the device tree, and remove now dead
code and types.

Signed-off-by: David Daney <david.daney@cavium.com>
Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>