spi: renesas,sh-msiof: Fix 'unevaluatedProperties' warnings

With 'unevaluatedProperties' support implemented, there's a number of
warnings when running dtbs_check:

arch/arm64/boot/dts/renesas/r8a77951-ulcb-kf.dtb: spi@e6e90000: Unevaluated properties are not allowed ('power-domains', 'resets' were unexpected)
	From schema: Documentation/devicetree/bindings/spi/renesas,sh-msiof.yaml

The main problem is that SoC DTSI's include power-domains and resets
property, whereas the renesas,sh-msiof.yaml has 'unevaluatedProperties:
false'. So just add optional power-domains and resets properties.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20220829220334.6379-1-prabhakar.mahadev-lad.rj@bp.renesas.com


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