usb: xceiv: create nop-usb-xceiv.h and avoid pollution on otg.h

nop-usb-xceiv was polluting otg.h with its own
function prototypes. Move those prototypes to
a nop-usb-xceiv.h header.

Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/arch/arm/mach-omap2/board-omap3evm.c b/arch/arm/mach-omap2/board-omap3evm.c
index ef230a0..9894e3d 100644
--- a/arch/arm/mach-omap2/board-omap3evm.c
+++ b/arch/arm/mach-omap2/board-omap3evm.c
@@ -32,6 +32,7 @@
 #include <linux/spi/ads7846.h>
 #include <linux/i2c/twl.h>
 #include <linux/usb/otg.h>
+#include <linux/usb/nop-usb-xceiv.h>
 #include <linux/smsc911x.h>
 
 #include <linux/wl12xx.h>