spi: rspi: Constify platform_device_id

The platform_device_id is not modified by the driver and core uses it as
const.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski.k@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-rspi.c

@@ -1300,7 +1300,7 @@ error1:
 	return ret;
 }
 
-static struct platform_device_id spi_driver_ids[] = {
+static const struct platform_device_id spi_driver_ids[] = {
 	{ "rspi",	(kernel_ulong_t)&rspi_ops },
 	{ "rspi-rz",	(kernel_ulong_t)&rspi_rz_ops },
 	{ "qspi",	(kernel_ulong_t)&qspi_ops },