Regulators should not be placed under simple-bus.

Move it outside simple-bus to fix the following schema warnings:

regulators: $nodename:0: 'regulators' does not match '^([a-z][a-z0-9\\-]+-bus|bus|localbus|soc|axi|ahb|apb)(@.+)?$'
From schema: site-packages/dtschema/schemas/simple-bus.yaml
Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>