[PATCH] zd1211rw: Add LED support

This patch includes a big cleanup of the existing unused LED code,
and adds support for controlling the LED.

The link LED will blink if the device is not associated. The LED
switches between 2 seconds on and 1 second off. If the device is
associated the LED is switched on.

The link LED also indicates packet TX. I do a little bit more led
resetting than the vendor driver, but the device works now as
expected for single LED and double LED devices.

Signed-off-by: Ulrich Kunitz <kune@deine-taler.de>
Signed-off-by: Daniel Drake <dsd@gentoo.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>