spi: Add support for Renesas CSI

The RZ/V2M SoC comes with the Clocked Serial Interface (CSI)
IP, which is a master/slave SPI controller.

This commit adds a driver to support CSI master mode.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Link: https://lore.kernel.org/r/Message-Id

: <20230622113341.657842-4-fabrizio.castro.jz@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>