USB: ohci: da8xx: Add wrappers for platform callbacks

To migrate to a DT based boot, we will remove the use of platform
callbacks, in favor of using the regulator framework to handle
vbus and over current.

In preparation to use a regulator instead of callbacks, move the platform
data callbacks into separate functions. This provides well defined place
to for the regulator API to coexist with the platform callbacks before
all users are converted.

Signed-off-by: Axel Haslam <ahaslam@baylibre.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>