Regulators is not a bus, so drop incomplete simple-bus usage to fix dtbs
W=1 warning:

  Warning (simple_bus_reg): /regulators/gpio-regulator: missing or empty reg/ranges property
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230420075053.41976-9-krzysztof.kozlowski@linaro.org