spi: dw: Drop default number of CS setting

spi: dw: Drop default number of CS setting

DW APB/AHB SSI core now supports the procedure automatically detecting the
number of native chip-select lines. Thus there is no longer point in
defaulting to four CS if the platform doesn't specify the real number
especially seeing the default number didn't correspond to any original DW
APB/AHB databook.

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://lore.kernel.org/r/20240424150657.9678-5-fancer.lancer@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>