usb: chipidea: add host role

This adds EHCI host support to the chipidea driver. We want it to be
part of the hdrc driver and not a standalone (sub-)driver module, as
the structure of ehci-hcd.c suggests, so for chipidea controller we
hack it to not provide platform-related code, but only the ehci hcd.

The ehci-platform driver won't work for us here too, because the
controller uses the same registers for both device and host mode and
also otg-related bits, so it's not really possible to put ehci registers
into a separate resource.

This is not a pretty solution, but the alternative is exporting symbols
from the chipidea driver to a ehci-chipidea driver and doing all the
module refcounting.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/ehci-hcd.c

@@ -1246,6 +1246,13 @@ static int ehci_get_frame (struct usb_hcd *hcd)
 }
 
 /*-------------------------------------------------------------------------*/
+/*
+ * The EHCI in ChipIdea HDRC cannot be a separate module or device,
+ * because its registers (and irq) are shared between host/gadget/otg
+ * functions  and in order to facilitate role switching we cannot
+ * give the ehci driver exclusive access to those.
+ */
+#ifndef CHIPIDEA_EHCI
 
 MODULE_DESCRIPTION(DRIVER_DESC);
 MODULE_AUTHOR (DRIVER_AUTHOR);
@@ -1504,3 +1511,4 @@ static void __exit ehci_hcd_cleanup(void)
 }
 module_exit(ehci_hcd_cleanup);
 
+#endif /* CHIPIDEA_EHCI */