drivers: sensor: add icm42670 6-axis accelerometer driver

the icm42670 from Invensense/TDK is a 6-axis accelerometer with
gyroscope and temperature sensing capabilities.

this initial driver does not support the devices 2K FIFO or many of the
other advanced features. Instead, only basic features are implemented.

Signed-off-by: Mikkel Jakobsen <mikkel.aunsbjerg@escolifesciences.com>