ARM: dts: imx: sabrelite: add Dual Lite/Solo support

This makes the structure of Sabre Lite board files the same
as Sabre SD board files so that they are easier to compare.

By this, I mean that the majority of the file imx6q-sabrelite.dts
is moved to imx6qdl-sabrelite.dtsi so that both imx6q-sabrelite.dts
and imx6dl-sabrelite.dts can include it.

Now Sabre Lite has support for Dual Lite/Solo
processors.

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>