tests: ringbuffer modify a tesecase
tests: ringbuffer modify a tesecase

Update code comments in ringbuffer/src/main.c
modify a testcase to verify the address stored by ring buffer
is contiguous, and the size of every element is equal to the size of
pointer.

Signed-off-by: Ningx Zhao <b27bf4706dc5a221d2ce626ff9b89d8daf27fcdd@intel.com>

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