ARM: sunxi: dt: add EMAC aliases

ARM: sunxi: dt: add EMAC aliases

U-Boot uses the ethernet0 alias to locate the right node to fill in
the MAC address of the first ethernet interface. This patch adds the
alias on all the sunxi SoCs with EMAC. In this way, people using
ethernet in U-Boot (eg, for tftp) can keep a consistent address on both
U-Boot and Linux with no additional effort.

Signed-off-by: Emilio López <emilio@elopez.com.ar>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>