samples: Allow use of "CONTROLLER" postfix for LED and GPIO

Rework samples using LED and GPIO to enforce use of "CONTROLLER"
as LED and PGIO postifx.
Change impact all samples that could be run by boards yet moved to
GPIO node generations, which is only STM32 for now

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>