sunxi: Add Linksprite_pcDuino3_Nano board / defconfig

sunxi: Add Linksprite_pcDuino3_Nano board / defconfig

This is a low-cost Allwinner A20 board with Arduino-style GPIO headers;
it features 1G RAM, 4G NAND flash, 1 micro-SD, 2 USB sockets, 1 micro
USB socket for OTG and another for power in, HDMI, SATA, 5V power for
SATA devices, gigabit Ethernet, an IR receiver, 3.5mm audio out and a
MIPI camera connector.

Like the BananaPi, this board needs GMAC_TX_DELAY set to 3 in order for
GMAC to work reliably at gigabit speeds.

For more details, see: http://linux-sunxi.org/LinkSprite_pcDuino3_Nano

Signed-off-by: Adam Sampson <ats@offog.org>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>