mmc: sdhci_am654: Constify struct regmap_config

`sdhci_am654_regmap_config` is not modified and can be declared as const
to move its data to a read-only section.
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://lore.kernel.org/r/20240705-sdhci_am654-const-regmap_config-v1-1-c166a8d48a66@gmail.comSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci_am654.c

@@ -90,7 +90,7 @@
 /* Command Queue Host Controller Interface Base address */
 #define SDHCI_AM654_CQE_BASE_ADDR 0x200
 
-static struct regmap_config sdhci_am654_regmap_config = {
+static const struct regmap_config sdhci_am654_regmap_config = {
 	.reg_bits = 32,
 	.val_bits = 32,
 	.reg_stride = 4,