dt-bindings: Remove leading 0x from bindings notation

Improve the binding example by removing all the leading 0x to fix the
following dtc warnings:

Warning (unit_address_format): Node /XXX unit name should not have leading "0x"

Converted using the following command:

find Documentation/devicetree/bindings -name "*.txt" -exec sed -i -e 's/([^ ])\@0x([0-9a-f])/$1\@$2/g' {} +

This is a follow up to commit 48c926cd



Signed-off-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Rob Herring <robh@kernel.org>