Refactor RSPI (on SH) DMA handling to make it reusable for other RSPI
implementations:
  - Call the DMA routines after configuring the TX Mode bit and after
    calling rspi_receive_init(), so these RSPI-specific operations can be
    removed from the DMA routines,
  - Absorb rspi_transfer_out_in() into rspi_transfer_one().
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NMark Brown <broonie@linaro.org>