This updates the documentation of all the NXP boards to use
the new `zephyr:board::` directive.
Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>
With over a dozen LED samples, grouping them in a common drivers/led/
folder helps keep things tidy and lays the groundwork for further
improvements in the way samples are showing up in the docs.
Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>