ARM: sunxi: Add functions to set pin drive levels

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
ARM: sunxi: Enable support for gigabit PHYs

GMAC on cubietruck uses a gigabit PHY.
Enable gigabit PHY support so auto-negotiation is correct.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
ARM: sunxi: Set drive level for GMAC pins

GMAC requires a higher drive level for gigabit speeds.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>