kernel: init: exclude unreachable code
kernel: init: exclude unreachable code

LCOV/gcovr doesn't understand what CODE_UNREACHABLE means.
Adding LCOV_EXCL_LINE to the macro definition unfortunately
doesn't work.

Exclude a bit of code which spins endlessly when multi-
threading is disabled that runs after the coverage report
is dumped.

Signed-off-by: Andrew Boie <aab045b28152628be6af0e556050d0381fd0a34d@intel.com>

GiulianoFranchetto/zephyr,Vudentz/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,galak/zephyr,nashif/zephyr,galak/zephyr,Vudentz/zephyr,galak/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,Vudentz/zephyr,nashif/zephyr,nashif/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr