ARM: dts: sunxi: Add a olinuxino-lime2-emmc

There are 3 kinds of OLinuXino Lime2 boards.
One without any on board storage, one with NAND storage and one with
eMMC storage. This patch adds the eMMC variant of boards.

eMMC storage is different from a regular SD card in that it is soldered
on the board and cannot be changed. Additionally, it shares pins with
the NAND module and with the second SPI port.

Signed-off-by: Olliver Schinagl <oliver@schinagl.nl>
[Maxime: Removed the change log from the commit log]
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>