Convert the fsl,ls-extirq binding to the new YAML format.

In contrast to the original binding documentation, there are three
compatibles which are used in their corresponding device trees which
have a specific compatible and the (already documented) fallback
compatible:
 - "fsl,ls1046a-extirq", "fsl,ls1043a-extirq"
 - "fsl,ls2080a-extirq", "fsl,ls1088a-extirq"
 - "fsl,lx2160a-extirq", "fsl,ls1088a-extirq"

Depending on the number of the number of the external IRQs which is
usually 12 except for the LS1021A where there are only 6, the
interrupt-map-mask was reduced from 0xffffffff to 0xf and 0x7
respectively and the number of interrupt-map entries have to
match.
Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220427075338.1156449-4-michael@walle.cc