usb: musb: tusb6010: fix compilation

earlier commits have broken compilation of
tusb6010 glue layer, fix it.

Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/tusb6010.c

@@ -18,6 +18,7 @@
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/init.h>
+#include <linux/prefetch.h>
 #include <linux/usb.h>
 #include <linux/irq.h>
 #include <linux/platform_device.h>