Staging: iio: add digital compass hmc5843 driver

Adding support for the Honeywell HMC5843. The interface to the device is
i2c

TODO:
Adding the documentation

Signed-off-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/staging/iio/Kconfig b/drivers/staging/iio/Kconfig
index b0e6244..569b938 100644
--- a/drivers/staging/iio/Kconfig
+++ b/drivers/staging/iio/Kconfig
@@ -44,6 +44,7 @@
 source "drivers/staging/iio/gyro/Kconfig"
 source "drivers/staging/iio/imu/Kconfig"
 source "drivers/staging/iio/light/Kconfig"
+source "drivers/staging/iio/magnetometer/Kconfig"
 
 source "drivers/staging/iio/trigger/Kconfig"