samples: yaml: filter can be limited to GPIO_CONTROLLER

It is safe to assume that if X_GPIO_CONTROLLER is defined (hence
generated) X_GPIO_PIN should also be defined.
If this is not the case, this is an issue and letting the sample
build will reveal the issue.
Update the yaml filter to rely only on _GPIO_CONTROLLER #define's


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