spi: renesas,sh-msiof: Add r8a779h0 support

Document support for the Clock-Synchronized Serial Interface with FIFO
(MSIOF) in the Renesas R-Car V4M (R8A779H0) SoC.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/68a4d8ad8638c1133e21d0eef87e8982ddea3dd8.1713279687.git.geert+renesas@glider.be


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