iio: accel: Add support for Domintech DMARD06 accelerometer

This patch add support for Domintech DMARD05, DMARD06 and DMARD07
accelerometers.

Signed-off-by: Aleksei Mamlin <mamlinav@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>