usb: xhci: move xhci.h to include usb

The xhci.h header file is currently located under drivers/usb/xhci
Move it to the include/usb folder to make it available to drivers that
are not under drivers/usb/xhci

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
diff --git a/drivers/usb/phy/omap_usb_phy.c b/drivers/usb/phy/omap_usb_phy.c
index 32e5bbb..897e6f1 100644
--- a/drivers/usb/phy/omap_usb_phy.c
+++ b/drivers/usb/phy/omap_usb_phy.c
@@ -19,7 +19,7 @@
 #include <linux/usb/dwc3.h>
 #include <linux/usb/xhci-omap.h>
 
-#include "../host/xhci.h"
+#include <usb/xhci.h>
 
 #ifdef CONFIG_OMAP_USB3PHY1_HOST
 struct usb3_dpll_params {