spi: fsl-spi: Make of_device_id array const

Make of_device_id array const, because all OF functions handle
it as const.

Signed-off-by: Jingoo Han <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

drivers/spi/spi-fsl-spi.c

···
 	.type = TYPE_GRLIB,
 };
 
-static struct of_device_id of_fsl_spi_match[] = {
+static const struct of_device_id of_fsl_spi_match[] = {
 	{
 		.compatible = "fsl,spi",
 		.data = &of_fsl_spi_fsl_config,