sensor: lis3mdl: remove use of i2c_burst_write api

i2c_burst_write API implementation in some driver
and generate a sequence of messages that does not allow to
communicate with LIS3MDL sensor. This commit replaces use
of i2c_burst_write with a call to i2c_write, which enables
sensor configuration.
Meanwhile, description of LIS3MDL is completed in sensor
header file.

Change-Id: Ib1b4643365f3c70b31fbfc4b0c30cff294b475a3
Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>