ARM: OMAP2+: Introduce local usb.h

Let's move what we can from plat/usb.h to the local usb.h
for ARM common zImage support.

This is needed so we can remove plat/usb.h for ARM common
zImage support.

Cc: Samuel Ortiz <sameo@linux.intel.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Partha Basak <parthab@india.ti.com>
Cc: Keshava Munegowda <keshava_mgowda@ti.com>
Cc: linux-usb@vger.kernel.org
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/usb-host.c

@@ -25,10 +25,10 @@
 
 #include <asm/io.h>
 
-#include <plat/usb.h>
 #include <plat/omap_device.h>
 
 #include "mux.h"
+#include "usb.h"
 
 #ifdef CONFIG_MFD_OMAP_USB_HOST