dt-bindings: misc: qcom,fastrpc: increase allowed iommus entries

The fastrpc components on the SM8550 SoC can require up to 3 IOMMU
entries, this bumps the maxItems to 3 for this purpose.

Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20221125071405.148786-2-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>