realtek: re-enable sfp driver for ZyXEL GS1900-10HP

realtek: re-enable sfp driver for ZyXEL GS1900-10HP

There is no need to define a static link or a phy for the sfp
ports.  Using phy-mode and managed properties to  describe the
link to the sfp phy.

We have to keep the now unconnected virtual "phys" because the
switch  driver uses their "phy-is-integrated" property to figure
out which ports to enable as fibre ports.

Acked-by: Birger Koblitz <mail@birger-koblitz.de>
Signed-off-by: Bjørn Mork <bjorn@mork.no>
(cherry picked from commit e8d391bd4650418182d96ca06ccd10d636efcbc3)