USB: host: ohci-at91: merge ohci_at91_of_init in ohci_hcd_at91_drv_probe

As device tree support is now mandatory, merge ohci_at91_of_init() in
ohci_hcd_at91_drv_probe().

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>