dt-bindings: mfd: hisilicon,hi6421-spmi-pmic: Fix regulator binding

dt-bindings: mfd: hisilicon,hi6421-spmi-pmic: Fix regulator binding

The regulator child nodes do not have unit addresses so drop the
incorrect '#address-cells' and '#size-cells' properties from the parent
'regulators' node.

Fixes: 352335a6aced ("staging: hikey9xx: hisilicon, hi6421-spmi-pmic.yaml: simplify props")
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20231206111754.7410-3-johan+linaro@kernel.org
Signed-off-by: Lee Jones <lee@kernel.org>