USB: OHCI: make ohci-platform a separate driver

This patch splits the ohci-platform code from ohci-hcd out
into its own separate driver module.This work is part of enabling
multi-platform kernels on ARM.

In V2:
  -Passed "hcd" argument instead of "ohci" in ohci_setup() because it is
   using "struct usb_hcd" argument.
In V3:
  -Directly passed "hcd" argument not required to call ohci_to_hcd() function.

Signed-off-by: Manjunath Goudar <manjunath.goudar@linaro.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>