mfd: Declare abx500_remove_ops()

Otherwise sparse warns about a public symbol with no declaration and
the compiler can't spot if the callers and users have different signatures
for the function.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

include/linux/mfd/abx500.h

@@ -229,4 +229,5 @@ struct abx500_ops {
 };
 
 int abx500_register_ops(struct device *core_dev, struct abx500_ops *ops);
+void abx500_remove_ops(struct device *dev);
 #endif