soc: sunxi: sram: Constify struct regmap_config

`sunxi_sram_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 <[e-mail]>
Reviewed-by: Andre Przywara <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Chen-Yu Tsai <[e-mail]>

drivers/soc/sunxi/sunxi_sram.c

···
 	spin_unlock(lock);
 }
 
-static struct regmap_config sunxi_sram_regmap_config = {
+static const struct regmap_config sunxi_sram_regmap_config = {
 	.reg_bits       = 32,
 	.val_bits       = 32,
 	.reg_stride     = 4,