phylib: make phy_scan_fixups() static

phy_scan_fixups()  isn't and shouldn't be called by the drivers directly, so
unexport it. And since Florian Fainelli's recent patches, the function is only
called locally, so we can make it static as well.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>