ARM: dts: s5pv210: move fixed regulators under root node in Aquila

The fixed regulators are kept under dedicated "regulators" node but this
causes multiple dtschema warnings:

  regulators: $nodename:0: 'regulators' does not match '^([a-z][a-z0-9\\-]+-bus|bus|soc|axi|ahb|apb)(@[0-9a-f]+)?$'
  regulators: #size-cells:0:0: 0 is not one of [1, 2]
  regulators: fixed-regulator@0:reg:0: [0] is too short
  regulators: fixed-regulator@1:reg:0: [1] is too short
  regulators: fixed-regulator@2:reg:0: [2] is too short

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200907161141.31034-21-krzk@kernel.org