mfd: axp20x: Fix duplicate const for model names

Replace duplicated const keyword for 'axp20x_model_names' with proper
array of const pointers to const strings.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/axp20x.c

@@ -29,7 +29,7 @@
 
 #define AXP20X_OFF	0x80
 
-static const char const *axp20x_model_names[] = {
+static const char * const axp20x_model_names[] = {
 	"AXP202",
 	"AXP209",
 	"AXP288",