net: mvmdio: make orion_mdio_wait_ready consistent

Amend orion_mdio_wait_ready so that the same timeout is used when
polling or using wait_event_timeout.  Set the timeout to 1ms.

Replace udelay with usleep_range to avoid a busy loop, and set the
polling interval range as 45us to 55us, so that the first sleep
will be enough in almost all cases.

Generate the same log message at timeout when polling or using
wait_event_timeout.

Signed-off-by: Leigh Brown <leigh@solinno.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>