Atmel : usb : add EHCI driver for Atmel SoC

Some Atmel SoC support USB EHCI, add the EHCI driver to support it.

To enable the USB EHCI, add the following configuration options into
board relative configuration file and remove USB OHCI options.

    #define CONFIG_USB_EHCI
    #define CONFIG_USB_EHCI_ATMEL
    #define CONFIG_SYS_USB_EHCI_MAX_ROOT_PORTS     2

Signed-off-by: Bo Shen <voice.shen@atmel.com>
Acked-by: Marek Vasut <marex@denx.de>
Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>
diff --git a/drivers/usb/host/Makefile b/drivers/usb/host/Makefile
index 59c3e57..4547f37 100644
--- a/drivers/usb/host/Makefile
+++ b/drivers/usb/host/Makefile
@@ -36,6 +36,7 @@
 # echi
 COBJS-$(CONFIG_USB_EHCI) += ehci-hcd.o
 COBJS-$(CONFIG_USB_EHCI_ARMADA100) += ehci-armada100.o utmi-armada100.o
+COBJS-$(CONFIG_USB_EHCI_ATMEL) += ehci-atmel.o
 ifdef CONFIG_MPC512X
 COBJS-$(CONFIG_USB_EHCI_FSL) += ehci-mpc512x.o
 else