dt-bindings: arm: Convert SPEAr board/soc bindings to json-schema

Convert SPEAr SoC bindings to DT schema format using json-schema.

Cc: Shiraz Hashim <shiraz.linux.kernel@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: devicetree@vger.kernel.org
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>