arm: socfpga: Do not enable gmac1 in Cyclone V dtsi

arm: socfpga: Do not enable gmac1 in Cyclone V dtsi

The GMAC which is enabled is purely board property, so do not enable
arbitrary GMAC in DT include files. Same goes for PHY mode, which is
again a board property. The CycloneV SoCDK does this correctly, but
SoCrates doesn't. This bug never manifested itself though, since all
the boards ever used the GMAC1 . This bug manifests itself only on
boards that utilise GMAC0.

Signed-off-by: Marek Vasut <marex@denx.de>