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/Makefile b/drivers/staging/iio/Makefile
index fff717e..e909674 100644
--- a/drivers/staging/iio/Makefile
+++ b/drivers/staging/iio/Makefile
@@ -15,3 +15,4 @@
 obj-y += imu/
 obj-y += light/
 obj-y += trigger/
+obj-y += magnetometer/