kconfig: Hide the Stellaris serial driver on unsupported platforms
kconfig: Hide the Stellaris serial driver on unsupported platforms

Hide the Stellaris serial driver on unsupported platforms.

Signed-off-by: Sebastian Bøe <edee888afd63e94916688495334700803eba20a0@nordicsemi.no>

GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,Vudentz/zephyr,explora26/zephyr,nashif/zephyr,punitvara/zephyr,explora26/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,Vudentz/zephyr,explora26/zephyr,punitvara/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,galak/zephyr,galak/zephyr,nashif/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,nashif/zephyr,ldts/zephyr,punitvara/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,explora26/zephyr,punitvara/zephyr,finikorg/zephyr,finikorg/zephyr,ldts/zephyr