spi: sh-msiof: add generic Gen4 binding

No further changes in this generation discovered yet.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20220824094327.33685-3-wsa+renesas@sang-engineering.com


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