spi: Convert bcm63xx-hsspi bindings to json-schema

This is the preparation for updates on the bcm63xx hsspi driver. Convert
the text based bindings to json-schema per new dts requirement.

Signed-off-by: William Zhang <william.zhang@broadcom.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Link: https://lore.kernel.org/r/20230207065826.285013-2-william.zhang@broadcom.com


Signed-off-by: Mark Brown <broonie@kernel.org>