The "spi" parameters of spi_get_chipselect() and spi_get_csgpiod() can
be const.

Fixes: 303feb3c ("spi: Add APIs in spi core to set/get spi->chip_select and spi->cs_gpiod")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/b112de79e7a1e9095a3b6ff22b639f39e39d7748.1678704562.git.geert+renesas@glider.beSigned-off-by: Mark Brown <broonie@kernel.org>