ARM: dts: imx6ul-isiot: Move common nodes in imx6ul-isiot.dtsi

Maintaining separate dtsi file with common nodes make unclear and
confusing since -isiot.dtsi is available for adding common nodes.
If the nodes are common between the dts files then mark status
as "okay" otherwise mark it "disabled" so-that respective dts
can mark status "okay"

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>