iio: gyro: bmi055 gyro sensor driver

Add support for the BMI055 gyroscope sensor. BMI055 is a package
consisting of an acceleration sensor and a gyroscope. This patch
adds support for the gyroscope only.

Spec downloaded from:
http://ae-bst.resource.bosch.com/media/products/dokumente/bmi055/BST-BMI055-DS000-06.pdf

The BMI055 gyroscope uses the same register definition as BMG160,
but does not specify a temp register. However, the temp register
seems to be working in the same way as for BMG160, so this patch
does not remove the temp channel for BMI055.

Signed-off-by: Irina Tirdea <irina.tirdea@intel.com>
Reviewed-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>