USB: EHCI: make ehci-atmel a separate driver

Separate the Atmel 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;
however, note that other changes are still needed before Atmel can be
booted with a multi-platform kernel. This is currently planned for
Linux-3.11.

With the infrastructure added by Alan Stern in patch 3e023203
"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 Atmel bus glue.

In V4 (arnd):
 - reordered #include statements.
 - removed call to ehci_shutdown and the corresponding export

In V3:
 - Detailed commit message added here about why this patch is required.
 - Replaced hcd_name string "ehci-atmel" to "atmel-ehci".
 - Inserted blank line in the Makefile to separate the EHCI drivers from
   the following non-EHCI drivers.
 - Exported ehci_shutdown symbol as it is needed by the Atmel driver.
 - Eliminated ehci_atmel_setup routine because hcd registers
   can be directly set in the ehci_atmel_drv_probe function.

In V2:
  Resolved below compiler error.
  drivers/usb/host/ehci-atmel.c: In function 'ehci_atmel_drv_remove':
  drivers/usb/host/ehci-atmel.c:167: error: implicit declaration of function 'ehci_shutdown'

Signed-off-by: Manjunath Goudar <manjunath.goudar@linaro.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Andrew Victor <linux@maxim.org.za>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>