spi: meson: Constify struct regmap_config

The regmap_config struct may be const because it is not modified by the
driver and regmap_init() accepts pointer to const.
Signed-off-by: NKrzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: NMark Brown <broonie@kernel.org>

drivers/spi/spi-meson-spifc.c

@@ -85,7 +85,7 @@ struct meson_spifc {
 	struct device *dev;
 };
 
-static struct regmap_config spifc_regmap_config = {
+static const struct regmap_config spifc_regmap_config = {
 	.reg_bits = 32,
 	.val_bits = 32,
 	.reg_stride = 4,