dt-bindings: riscv: microchip: document icicle reference design

dt-bindings: riscv: microchip: document icicle reference design

The icicle kit reference design's v2022.09 release made some changes
to the memory map - including adding the ability to read the fabric
clock controllers via the system controller bus & making the PCI
controller work with upstream Linux.

While the PCI was not working in the v2022.03 design, so nothing is
broken there in terms of backwards compatibility, the fabric clocks
used in the v2022.03 design were chosen by the individual run of the
synthesis tool. In the v2022.09 reference design, the clocks are fixed
to use the "north west" fabric Clock Conditioning Circuitry.

In the v2022.10 release, the memory map on the DDR side is also
changing, so to avoid making a breaking change here twice, jump over the
v2022.09 release and straight to the v2022.10 one.

Make use of a new compatible to denote that v2022.{09,10} reference
design releases are not backwards compatible.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>