net: phy: expose phy_aneg_done API for use by drivers

Make phy_aneg_done() available to drivers so that the result of the
auto-negotiation initiated by phy_start_aneg() can be determined.

Remove the local implementation of phy_aneg_done() from the Aeroflex
driver and use the phy library version.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>