libertas: remove handling for CMD_802_11_LED_GPIO_CTRL

... which just resided as an old-style command in cmd/cmdresp, but
was nowhere useed. If we ever need it, we can re-add it as a newstyle
command.

Signed-off-by: Holger Schurig <hs4233@mail.mn-solutions.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>