USB: musb: fix musb_platform_set_mode() definition

Update function definition to match latest MUSB framework.
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Cliff Cai <cliff.cai@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Anand Gadiyar <gadiyar@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/musb/blackfin.c

@@ -226,8 +226,9 @@ int musb_platform_get_vbus_status(struct musb *musb)
 	return 0;
 }
 
-void musb_platform_set_mode(struct musb *musb, u8 musb_mode)
+int musb_platform_set_mode(struct musb *musb, u8 musb_mode)
 {
+	return -EIO;
 }
 
 int __init musb_platform_init(struct musb *musb)