staging: iio: add support for hmc5883/hmc5883l to hmc5843 magnetometer driver

v3 addresses review comments:
* rotate tables (Jonathan Cameron)
* remove trailing space, add newline in sysfs output (Jonathan Cameron)
* split out patch for reorganization of hmc5843_set_rate() (Jonathan Cameron)
* use static table to describe chip variants (Jonathan Cameron)

v2 addresses review comments:
* fixes and cleanups have been split out (Jonathan Cameron)
* constants are generally prefixed HMC5843_, except when related
  specifically to hmc5883 (Jonathan Cameron)
* simplify code and avoid temp buffer in
  hmc5843_show_sampling_frequencies_available() (Lars-Peter Clausen)
* use sysfs_streq() instead of strncmp()/strlen() in
  hmc5843_check_sampling_frequency() (Lars-Peter Clausen)
Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/iio/magnetometer/Kconfig

@@ -15,13 +15,13 @@ config SENSORS_AK8975
 	  will be called ak8975.
 
 config SENSORS_HMC5843
-	tristate "Honeywell HMC5843 3-Axis Magnetometer"
+	tristate "Honeywell HMC5843/5883/5883L 3-Axis Magnetometer"
 	depends on I2C
 	help
-	  Say Y here to add support for the Honeywell HMC 5843 3-Axis
-	  Magnetometer (digital compass).
+	  Say Y here to add support for the Honeywell HMC5843, HMC5883 and
+	  HMC5883L 3-Axis Magnetometer (digital compass).
 
 	  To compile this driver as a module, choose M here: the module
-	  will be called hmc5843
+	  will be called hmc5843.
 
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