ixgbe: fix issues with failing to detect insert of unsupported module

Several small fixes around negative test case of the insertion of a
IXGBE_ERR_NOT_SUPPORTED module.

- mdio45_probe call was always failing due to mdio.prtad not being
set.  The function set to mdio.mdio_read was still working as we just
happen to always be at prtad == 0.  This will allow us to set the phy_id
and phy.type correctly now.

- There was timing issue with i2c calls when initiated from a tasklet.
A small delay was added to allow the electrical oscillation to calm down.

- Logic change in ixgbe_sfp_task that allows NOT_SUPPORTED condition
to be recognized.

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>