USB: OHCI: make ohci-da8xx a separate driver

Separate the Davinci OHCI host controller driver from ohci-hcd
host code so that it can be built as a separate driver module.
This work is part of enabling multi-platform kernels on ARM

Tested-by: David Lechner <david@lechnology.com>
Signed-off-by: Manjunath Goudar <manjunath.goudar@linaro.org>
[Axel: adapted and rebased, fixed minor comments]
Signed-off-by: Axel Haslam <ahaslam@baylibre.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>