drivers: sensor: icm42605: Fix build issues

There are several different issues when trying to build the icm42605
sensor driver:

* Missing entry in drivers/sensor/CMakeLists.txt
* Issues with #ifndef in header files
* Issues with const usage
* Missing function prototypes in headers
* Fix use of LOG_MODULE_REGISTER v LOG_MODULE_DECLARE
* Add missing dts node to tests/drivers/build_all/spi.dtsi

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>