MAINTAINERS: Remove self from PHY LIBRARY

My last significant achievements to the PHY library was ensuring we
would have small bus factor by having Andrew and Heiner added. The world
has moved on past 1G, but I have not, so let more competent maintainers
take over.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>