Merge branch 'ksz-switch-refclk'

Merge branch 'ksz-switch-refclk'

Robert Hancock says:

====================
Allow disabling KSZ switch refclock

The reference clock output from the KSZ9477 and related Microchip
switch devices is not required on all board designs. Add a device
tree property to disable it for power and EMI reasons.

Changes since v3:
-rework some code for simplicity

Changes since v2:
-check for conflicting options in DT, added note in bindings doc

Changes since v1:
-added Acked-by on patch 1, rebase to net-next
====================

Signed-off-by: David S. Miller <davem@davemloft.net>