leds: various: compile if COMPILE_TEST=y

These drivers can be compiled without modification when COMPILE_TEST=y:
  cobalt-qube, cobalt-raq, netxbig, ns2 and s3c24xx

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Dan Murphy <dmurphy@ti.com>
Signed-off-by: Pavel Machek <pavel@ucw.cz>