iio:magnetometer:bmc150_magn: add regmap dependency

bmc150_magn makes use of REGMAP_I2C, so select it to build always without
errors.

Fixes: c91746a2 ("iio: magn: Add support for BMC150 magnetometer")
Signed-off-by: Hartmut Knaack <knaack.h@gmx.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/magnetometer/Kconfig

@@ -90,6 +90,7 @@ config IIO_ST_MAGN_SPI_3AXIS
 config BMC150_MAGN
 	tristate "Bosch BMC150 Magnetometer Driver"
 	depends on I2C
+	select REGMAP_I2C
 	select IIO_BUFFER
 	select IIO_TRIGGERED_BUFFER
 	help