USB: host: ohci-at91: move at91_usbh_data definition in c file

Move struct at91_usbh_data back in ohci-at91.c as this is the only user
left after switching all at91 platforms to DT only.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>