iio:light:ltr501: fix regmap dependency

The use of regmap in commit 2f2c96338afc requires REGMAP_I2C to be selected, in
order to meet all dependencies.

Fixes: 2f2c96338afc ("iio: ltr501: Add regmap support.")

Signed-off-by: Hartmut Knaack <[e-mail]>
Acked-by: Daniel Baluta <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/light/Kconfig

···
 config LTR501
 	tristate "LTR-501ALS-01 light sensor"
 	depends on I2C
+	select REGMAP_I2C
 	select IIO_BUFFER
 	select IIO_TRIGGERED_BUFFER
 	help