usb: host: xhci: add a platform-private field

This patch adds an xhci->priv field for private use by
XHCI platform drivers. Until now none of the platform drivers
has used this private space.
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci.h

@@ -1656,6 +1656,9 @@ struct xhci_hcd {
 	u32			port_status_u0;
 /* Compliance Mode Timer Triggered every 2 seconds */
 #define COMP_MODE_RCVRY_MSECS 2000
+
+	/* platform-specific data -- must come last */
+	unsigned long		priv[0] __aligned(sizeof(s64));
 };
 
 /* Platform specific overrides to generic XHCI hc_driver ops */