USB: EHCI: make ehci-orion a separate driver

USB: EHCI: make ehci-orion a separate driver

Separate the Orion host controller driver from ehci-hcd host
code into its own driver module because of following reason.

With the multiplatform changes in arm-soc tree, it becomes
possible to enable the mvebu platform (which uses
ehci-orion) at the same time as other platforms that require
a conflicting EHCI bus glue. At the moment, this results
in a warning like

drivers/usb/host/ehci-hcd.c:1297:0: warning: "PLATFORM_DRIVER" redefined [enabled by default]
drivers/usb/host/ehci-hcd.c:1277:0: note: this is the location of the previous definition
drivers/usb/host/ehci-orion.c:334:31: warning: 'ehci_orion_driver' defined but not used [-Wunused-variable]

and an ehci driver that only works on one of them.

With the infrastructure added by Alan Stern in patch 3e0232039
"USB: EHCI: prepare to make ehci-hcd a library module", we can
avoid this problem by turning a bus glue into a separate
module, as we do here for the orion bus glue.

An earlier version of this patch was included in 3.9 but caused
a regression there, which has subsequently been fixed.

While we are here, use the opportunity to disabiguate the two
Marvell EHCI controller implementations in Kconfig.

In V4 (arnd):
- Improve Kconfig text

In V3:
- More detail provided in commit message regarding this patch.
- Replaced hcd_name string "ehci-orion" into "orion-ehci".
- MODULE_LICENSE is GPL v2.
- In ehci_init_driver calling second argument passed  as NULL instead of
  ehci_orion_overrides because ehci_orion_overrides is removed.

In V2:
- Tegra patch related changes removed from this patch.

Signed-off-by: Manjunath Goudar <manjunath.goudar@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>