iio: light: gp2ap020a00f: Select REGMAP_I2C

This patch adds missing 'select' statement for gp2ap020a00f driver.
Without regmap_i2c, we get the following error when loading the module:
Unknown symbol devm_regmap_init_i2c.
Signed-off-by: NRoberta Dobrescu <roberta.dobrescu@gmail.com>
Reviewed-by: NDaniel Baluta <daniel.baluta@intel.com>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

drivers/iio/light/Kconfig

@@ -62,6 +62,7 @@ config CM36651
 config GP2AP020A00F
 	tristate "Sharp GP2AP020A00F Proximity/ALS sensor"
 	depends on I2C
+	select REGMAP_I2C
 	select IIO_BUFFER
 	select IIO_TRIGGERED_BUFFER
 	select IRQ_WORK