spi: spi-rspi: fix build error for the latest shdma driver

Because the latest shdma driver changed, it caused build error in
the spi-rspi driver. This patch fixed the build error.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>