dt-bindings: fsl: rcpm: Add 'little-endian' and update Chassis definition

By default, QorIQ SoC's RCPM register block is Big Endian. But
there are some exceptions, such as LS1088A and LS2088A, are
Little Endian. So add this optional property to help identify
them.

Actually LS2021A and other Layerscapes won't totally follow Chassis
2.1, so separate them from powerpc SoC.

Signed-off-by: Ran Wang <ran.wang_1@nxp.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Li Yang <leoyang.li@nxp.com>

Documentation: dt: binding: fsl: add devicetree binding for describing RCPM

RCPM is the Run Control and Power Management module performs all
device-level tasks associated with device run control and power
management.

Add this for freescale powerpc platform and layerscape platform.

Signed-off-by: Chenhui Zhao <chenhui.zhao@freescale.com>
Signed-off-by: Tang Yuantian <Yuantian.Tang@freescale.com>
Signed-off-by: Wang Dongsheng <dongsheng.wang@freescale.com>
[scottwood: s/pointer/phandle and "disabled" status from example]
Signed-off-by: Scott Wood <oss@buserror.net>