drivers: spi: CS configuration through devicetree

Add an additional option to the spi_cs_control struct that records how
the pin has been configured in devicetree. For drivers that are not
updated, the CS behaviour is the same as before (Push-Pull).

Use the devicetree knowledge with the GPIO subsystem so that the correct
physical pin levels for the CS pin are automatically selected.

Fixes #26267

Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>