dt-bindings: soc: bcm: bcm2835-pm: Convert bindings to DT schema

This converts the brcm,bcm2835-pm bindings from text to proper schema.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>