ARM: dts: qcom: pmx65: use node name "gpio" for spmi-gpio

All other usages of qcom,spmi-gpio use the gpio@ node name, and this is
also validated by the dt binding check. Fix it.

Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220925190622.111505-1-luca@z3ntu.xyz