phy: remove phy-supply related code

phy-supply is now handled at uclass level. Remove it from the drivers that
implement it at the driver level.

Acked-by: Neil Armstrong <neil.armstrong@linaro.org>
Suggested-by: Jonas Karlman <jonas@kwiboo.se>
Signed-off-by: Eugen Hristev <eugen.hristev@collabora.com>