dt-bindings: misc: qcom,fastrpc: correct qcom,nsessions name

The property in old TXT bindings, in Linux driver and in DTS is
qcom,nsessions.

Fixes: ed18a9b1 ("dt-bindings: misc: fastrpc convert bindings to yaml")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220909125403.803158-2-krzysztof.kozlowski@linaro.orgSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/misc/qcom,fastrpc.yaml

@@ -70,7 +70,7 @@ patternProperties:
       reg:
         maxItems: 1
 
-      qcom,nsession:
+      qcom,nsessions:
         $ref: /schemas/types.yaml#/definitions/uint32
         default: 1
         description: >