mfd: altera-a10sr: Make altr_a10sr_regmap_config static const

It's only used in this driver and never get modified, make it static const.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Reviewed-by: Thor Thayer <tthayer@opensource.altera.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/altera-a10sr.c b/drivers/mfd/altera-a10sr.c
index c05aa4f..40ed65e 100644
--- a/drivers/mfd/altera-a10sr.c
+++ b/drivers/mfd/altera-a10sr.c
@@ -94,7 +94,7 @@
 	}
 }
 
-const struct regmap_config altr_a10sr_regmap_config = {
+static const struct regmap_config altr_a10sr_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,