usb: ulpi: make ops struct constant

None of the core ulpi functions perform any changes to the operations
struct, and logically as a struct that contains function pointers
there's no reason it shouldn't be constant.

Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Tal Shorer <tal.shorer@gmail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
diff --git a/include/linux/ulpi/interface.h b/include/linux/ulpi/interface.h
index cdedac8..a2011a9 100644
--- a/include/linux/ulpi/interface.h
+++ b/include/linux/ulpi/interface.h
@@ -16,7 +16,7 @@
 	int (*write)(struct device *dev, u8 addr, u8 val);
 };
 
-struct ulpi *ulpi_register_interface(struct device *, struct ulpi_ops *);
+struct ulpi *ulpi_register_interface(struct device *, const struct ulpi_ops *);
 void ulpi_unregister_interface(struct ulpi *);
 
 #endif /* __LINUX_ULPI_INTERFACE_H */