spi: drop check for validity of device chip selects

Now that we know the number of chip selects of a device, we can assume
these are valid, and do not need to check them first.

Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Link: https://patch.msgid.link/20250915183725.219473-5-jonas.gorski@gmail.com


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