spi: Constify spi_get_ctldata()'s spi parameter

The "spi" parameter of spi_get_ctldata() can be const.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/8960e07adaad8d92d2c3aa045af9ee3c5d2130a8.1678704562.git.geert+renesas@glider.beSigned-off-by: Mark Brown <broonie@kernel.org>

include/linux/spi/spi.h

@@ -244,7 +244,7 @@ static inline void spi_dev_put(struct spi_device *spi)
 }
 
 /* ctldata is for the bus_controller driver's runtime state */
-static inline void *spi_get_ctldata(struct spi_device *spi)
+static inline void *spi_get_ctldata(const struct spi_device *spi)
 {
 	return spi->controller_state;
 }