iio: bmg160: Use i2c regmap instead of direct i2c access

This patch introduces regmap usage into the driver. This is done to
later easily support the SPI interface of this chip.
Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Reviewed-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/gyro/Kconfig

@@ -55,6 +55,7 @@ config BMG160
 	depends on I2C
 	select IIO_BUFFER
 	select IIO_TRIGGERED_BUFFER
+	select REGMAP_I2C
 	help
 	  Say yes here to build support for Bosch BMG160 Tri-axis Gyro Sensor
 	  driver. This driver also supports BMI055 gyroscope.