samples: flash_shell: print 16 bytes of flash
samples: flash_shell: print 16 bytes of flash

On large memory areas printing 8 bytes/line is not enough.
Increased printing 16 bytes per line.

Signed-off-by: Andrei Gansari <f1330555a90b7a22d81843f3c4366f58b50eae34@nxp.com>

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