ARM: dts: qcom: pmx55: align SPMI PMIC Power-on node name with dtschema

Bindings expect Power-on node name to be "pon":

  'power-on@800' do not match any of the regexes

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: David Heidelberg <david@ixit.cz>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Reviewed-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220828084341.112146-4-krzysztof.kozlowski@linaro.org