spi: rspi: Use NULL as the clock ID

There's only one RSPI/QSPI clock, so we can use NULL as the clock ID

Signed-off-by: Geert Uytterhoeven <geert+renesas@linux-m68k.org>
Signed-off-by: Mark Brown <broonie@linaro.org>

diff --cc drivers/spi/spi-rspi.c
Simple merge