linux-phytec-fsl

ARM: sunxi: Enable GMAC in sunxi_defconfig

Since the support of the GMAC has been merged, we're using it as the ethernet
controller on the A20 devices.

However, sunxi_defconfig wasn't selecting it hence breaking the NFS boot.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>