drivers:usb:fsl:Make fsl ehci drv an independent driver module

Make Freescale EHCI driver an independent entity from ehci-hcd.c.
This involves
	- using module_init/module_exit functions
	- using overrides structure
	- some necessary code cleanup

Signed-off-by: Ramneek Mehresh <ramneek.mehresh@freescale.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/Kconfig

@@ -137,7 +137,7 @@ config XPS_USB_HCD_XILINX
 		devices only.
 
 config USB_EHCI_FSL
-	bool "Support for Freescale PPC on-chip EHCI USB controller"
+	tristate "Support for Freescale PPC on-chip EHCI USB controller"
 	depends on FSL_SOC
 	select USB_EHCI_ROOT_HUB_TT
 	select USB_FSL_MPH_DR_OF if OF