drivers: flash: Restore write protection in flash_shell
drivers: flash: Restore write protection in flash_shell

Restore the flash write proectction after disabling it for
flash write and erase shell commands.

Signed-off-by: Ievgenii Meshcheriakov <df2064527cff29064d40b3c65720cad00a28b85e@nordicsemi.no>

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