ARM: sunxi: fix gpio drive mask

According to A10 user manual, the width of the drive configuration
for each pin is only 2 bits. Fix the mask so we don't touch values
for other pins.

Signed-off-by: Ma Haijun <mahaijuns@gmail.com>
Signed-off-by: Chen-Yu Tsau <wens@csie.org>
sunxi: Add gmac clock macros

Add macros for gmac clock control, instead of useing raw values.
Also add comment noting GMAC ahb gate is in second gate register,
to avoid confusion over same offset as EMAC.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
sunxi: Move GMAC init code to seperate file

GMAC init code now exists in a shim file under drivers/net, instead of
sunxi board initialization code. It has been cleaned up to use macros
for clock controls.

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