dt-bindings: net: qcom,ipa: IPA does support up to two iommus

Fix warnings as:
arch/arm/boot/dts/qcom-sdx55-mtp.dt.yaml: ipa@1e40000: iommus: [[21, 1504, 0], [21, 1506, 0]] is too long
	From schema: Documentation/devicetree/bindings/net/qcom,ipa.yaml
Signed-off-by: David Heidelberg <david@ixit.cz>
Reviewed-by: Alex Elder <elder@linaro.org>
Link: https://lore.kernel.org/r/20211026163240.131052-1-david@ixit.czSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/net/qcom,ipa.yaml

@@ -64,7 +64,8 @@ properties:
       - const: gsi
 
   iommus:
-    maxItems: 1
+    minItems: 1
+    maxItems: 2
 
   clocks:
     maxItems: 1