Merge branch 'add-mdiobus_modify_changed-helper'

Russell King says:

====================
Add mdiobus_modify_changed() helper

Sean Anderson's recent patch series is introducing more read-write
operations on the MDIO bus that only need to happen if a change is
being made.

We have similar logic in __mdiobus_modify_changed(), but we didn't
add its correponding locked variant mdiobus_modify_changed() as we
had very few users. Now that we are getting more, let's add the
helper.
====================

Link: https://lore.kernel.org/r/YV2UIa2eU+UjmWaE@shell.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>