fotg210: Make Xen notification consistent with EHCI

If CONFIG_XEN_DOM0 is enabled, the ehci-dbgp driver notifies Xen of
controller reset events via xen_dbgp_reset_prep() and
xen_dbgp_external_startup() (via calls to xen_dbgp_op().)  Otherwise
<linux/usb/ehci_def.h> defines them as no-ops to disable this logic.

The fotg210 driver copies much of the dbgp code from ehci_def.h, but it
unconditionally defines the Xen hooks as no-ops, effectively disabling
these notifications when CONFIG_EARLY_PRINTK_DBGP is disabled.  When
enabled, though, notifying Xen is dependent on CONFIG_XEN_DOM0 due to
fotg210 leveraging the ehci-dbgp driver.

The following table compares the implementations of xen_dbgp_reset_prep()
and xen_dbgp_external_startup() in the ehci-dbgp and fotg210 drivers
under the relevant configurations:

  EARLY_PRINTK_DBGP?  XEN_DOM0?  ehci-dbgp      fotg210
  ------------------  ---------  -------------  -------------
  n                   n          no-op          no-op
  n                   y          xen_dbgp_op()  no-op
  y                   n          no-op          no-op
  y                   y          xen_dbgp_op()  xen_dbgp_op()

This suggests that fotg210 is, at best, indifferent to whether Xen is
notified of these events.  Make fotg210 consistent with ehci-dbgp as a
step towards consolidating this code duplication.

Signed-off-by: Chris Rorvick <chris@rorvick.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/fotg210.h

@@ -326,6 +326,10 @@ extern struct console early_dbgp_console;
 
 struct usb_hcd;
 
+#ifdef CONFIG_XEN_DOM0
+extern int xen_dbgp_reset_prep(struct usb_hcd *);
+extern int xen_dbgp_external_startup(struct usb_hcd *);
+#else
 static inline int xen_dbgp_reset_prep(struct usb_hcd *hcd)
 {
 	return 1; /* Shouldn't this be 0? */
@@ -335,6 +339,7 @@ static inline int xen_dbgp_external_startup(struct usb_hcd *hcd)
 {
 	return -1;
 }
+#endif
 
 #ifdef CONFIG_EARLY_PRINTK_DBGP
 /* Call backs from fotg210 host driver to fotg210 debug driver */