ARM: dts: sun7i: cubieboard2: Enable GMAC instead of EMAC

The A20 has EMAC and GMAC multiplexed on the same pins.
GMAC has better performance via internal DMA, and fewer
hardware issues.
ARM: dts: sun7i: olinuxino-micro: Enable GMAC instead of EMAC

The A20 has EMAC and GMAC multiplexed on the same pins.
GMAC has better performance via internal DMA, and fewer
hardware issues.