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

Convert ST STi SoC bindings to DT schema format using json-schema.

Acked-by: Patrice Chotard <patrice.chotard@st.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: devicetree@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>