mfd: sun4i: Drop of_match_ptr from of_device_id table

The driver can match only via the DT table so the table should be always
used and the of_match_ptr does not have any sense (this also allows ACPI
matching via PRP0001, even though it is not relevant here). This fixes
compile warning (!CONFIG_OF on x86_64):

drivers/mfd/sun4i-gpadc.c:79:34: warning: ‘sun4i_gpadc_of_match’ defined but not used [-Wunused-const-variable=]

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>

drivers/mfd/sun4i-gpadc.c

···
 static struct platform_driver sun4i_gpadc_driver = {
 	.driver = {
 		.name = "sun4i-gpadc",
-		.of_match_table = of_match_ptr(sun4i_gpadc_of_match),
+		.of_match_table = sun4i_gpadc_of_match,
 	},
 	.probe = sun4i_gpadc_probe,
 };