iio:gyro: Add STMicroelectronics gyroscopes driver

This patch adds a generic gyroscope driver for STMicroelectronics
gyroscopes, currently it supports:
L3G4200D, LSM330DL, L3GD20, L3GD20H, LSM330DLC, L3G4IS, LSM330.

Signed-off-by: Denis Ciocca <denis.ciocca@st.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --cc drivers/iio/gyro/Kconfig
Simple merge

diff --cc drivers/iio/gyro/Makefile
Simple merge

diff --cc drivers/iio/gyro/st_gyro.h
Simple merge

diff --cc drivers/iio/gyro/st_gyro_buffer.c
Simple merge

diff --cc drivers/iio/gyro/st_gyro_core.c
Simple merge

diff --cc drivers/iio/gyro/st_gyro_i2c.c
Simple merge

diff --cc drivers/iio/gyro/st_gyro_spi.c
Simple merge