tests: board_shell: re-enable flash, ADC, and CAN shells
tests: board_shell: re-enable flash, ADC, and CAN shells

Re-enable flash, ADC, and CAN related shell commands in the
board_shell test application.

This fixes commit 965aac39b601ae8d07e7cc9da8867488547b6eff.

Signed-off-by: Henrik Brix Andersen <24a3f13c22635bab658e39fc5f1e63c575328aae@vestas.com>

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