ARM: dts: aspeed: rainier: Remove regulators

Regulators will be dynamically configured and monitored from userspace.

Signed-off-by: Matthew Barth <msbarth@linux.ibm.com>
Reviewed-by: Eddie James <eajames@linux.ibm.com>
Reviewed-by: Jim Wright <wrightj@linux.vnet.ibm.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>