net/rfkill/rfkill.c: fix build with CONFIG_RFKILL_LEDS=n

net/rfkill/rfkill.c: fix build with CONFIG_RFKILL_LEDS=n

net/rfkill/rfkill.c: In function 'update_rfkill_state':
net/rfkill/rfkill.c:99: error: implicit declaration of function 'rfkill_led_trigger'

Caused by

: commit 492301fb5d12e4a77a1010ad2b6f1ed306014123
: Author: Larry Finger <Larry.Finger@lwfinger.net>
: Date:   Thu Apr 9 22:14:19 2009 -0500
:
:     rfkill: Fix broken rfkill LED in 2.6.30-rc1

Cc: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Cc: Ivo van Doorn <IvDoorn@gmail.com>
Cc: Michael Buesch <mb@bu3sch.de>
Cc: David S. Miller <davem@davemloft.net>
Cc: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>