ARM: dts: qcom: mdm9615: populate vsdcc fixed regulator

Fixed regulator put under "regulators" node will not be populated,
unless simple-bus or something similar is used.  Drop the "regulators"
wrapper node to fix this.

Fixes: 2c5e5965

 ("ARM: dts: Add MDM9615 dtsi")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20230924183914.51414-3-krzysztof.kozlowski@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>