spi: rspi: provide port addresses to dmaengine driver via slave configuration

Don't rely on shdma dhaengine driver getting DMA slave addresses from its
slave configuration. Instead provide those addresses, using a
dmaengine_slave_config() call.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski+renesas@gmail.com>
Signed-off-by: Mark Brown <broonie@linaro.org>