usb: ohci-da8xx: remove unused callbacks from platform data

There are no more users of the platform_data callbacks in ohci-da8xx.
Remove them.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>