ARM: dts: imx6: Add initial support for phyBOARD-Mira

This patch adds basic support for PHYTEC phyBOARD-Mira as carrier board
for PHYTEC phyCORE-i.MX 6.

Signed-off-by: Christian Hemp <c.hemp@phytec.de>
Signed-off-by: Stefan Christ <s.christ@phytec.de>
Signed-off-by: Christoph Fritz <chf.fritz@googlemail.com>
Signed-off-by: Stefan Riedmueller <s.riedmueller@phytec.de>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>