spi-rockchip: Fix register out of bounds access

Do not write native chip select stuff for GPIO chip selects.
GPIOs can be numbered much higher than native CS.
Also, it makes no sense.

Signed-off-by: Luis de Arquer <luis.dearquer@inertim.com>
Link: https://patch.msgid.link/365ccddfba110549202b3520f4401a6a936e82a8.camel@gmail.com


Signed-off-by: Mark Brown <broonie@kernel.org>