usb, chipidea: fix link error when USB_EHCI_HCD is a module

Fixes link error when USB_EHCI_HCD=m and USB_CHIPIDEA_HOST=y:

	drivers/built-in.o: In function `ci_hdrc_host_init':
	drivers/usb/chipidea/host.c:104: undefined reference to `ehci_init_driver'

as a result of commit 09f6ffde2e ("USB: EHCI: fix build error by making
ChipIdea host a normal EHCI driver").

Cc: stable@vger.kernel.org [v3.7+]
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/chipidea/Kconfig

@@ -20,7 +20,7 @@ config USB_CHIPIDEA_UDC
 config USB_CHIPIDEA_HOST
 	bool "ChipIdea host controller"
 	depends on USB=y || USB=USB_CHIPIDEA
-	depends on USB_EHCI_HCD
+	depends on USB_EHCI_HCD=y
 	select USB_EHCI_ROOT_HUB_TT
 	help
 	  Say Y here to enable host controller functionality of the