logging: log_core.c: fix coding guideline 15.7 missing comment
logging: log_core.c: fix coding guideline 15.7 missing comment

The final else {} in the if...else if is missing required
comment (non-empty, ';' is not sufficient). This adds a comment
to comply with CG 15.7.

Signed-off-by: Jennifer Williams <7953176682adde4345743ea99dbf2682fb898b9d@intel.com>

finikorg/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr