drivers/rtc/rtc-isl12057.c: 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: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/rtc/rtc-isl12057.c

···
 	.alarm_irq_enable = isl12057_rtc_alarm_irq_enable,
 };
 
-static struct regmap_config isl12057_rtc_regmap_config = {
+static const struct regmap_config isl12057_rtc_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
 };