As the chip selects can be configured through ACPI/OF/swnode, and
the set_cs() callback will only be called when a native chip select
is being used, there is no reason for the driver to only support the
native chip select as the first chip select. Remove the check that
introduces this limitation.

Fixes: ef75e767 ("spi: cs42l43: Add SPI controller support")
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://msgid.link/r/20240306161004.2205113-1-ckeepax@opensource.cirrus.comSigned-off-by: Mark Brown <broonie@kernel.org>