spi: rspi: Replace spi_master by spi_controller

As of commit 8caab75f ('spi: Generalize SPI "master" to
"controller"'), the old master-centric names are compatibility wrappers
for the new controller-centric names.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@kernel.org>