USB: EHCI: make ehci-tegra a separate driver

Separate the Tegra on-chip host controller driver from
ehci-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.

Signed-off-by: Manjunath Goudar <manjunath.goudar@linaro.org>
[swarren, reworked Manjunath's patches to split them more logically,
minor re-order of added lines to better match layout of other split-up
HCD drivers and existing code, add MODULE_DEVICE_TABLE, fix
MODULE_LICENSE, adapted to change in earlier patches which removed the
ehci_driver_overrides addition, removed all PM code and solved circular
dependencies.]
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>