dt-bindings: spi: sh-msiof: Convert bindings to json-schema

Convert Renesas HSPI bindings documentation to json-schema.
Also name bindings documentation file according to the compat string
being documented.

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20190926102533.17829-1-horms+renesas@verge.net.au
Signed-off-by: Mark Brown <broonie@kernel.org>