net: phy: Decide on C45 capabilities based on presence of method

Some PHYs provide invalid IDs in C22 space. If C45 is supported on the
bus an attempt can be made to get the IDs from the C45 space. Decide
on this based on the presence of the C45 read method in the bus
structure. This will allow the unreliable probe_capabilities to be
removed.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>