ARM: dts: imx6: Add DFI FS700-M60 board support

The DFI FS700-M60 is a q7 board with i.MX6 quad, dual, duallite or solo
SoC. This adds support for it.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>