wireless: missing include in lib80211.h

wireless: missing include in lib80211.h

This patch adds #include <linux/timer.h> in lib80211.h to avoid
these compilation erros.

> In file included from /work/src/wireless-testing/net/wireless/lib80211.c:24:
> /work/src/wireless-testing/include/net/lib80211.h:113: error: field
> 'crypt_deinit_timer' has incomplete type
> /work/src/wireless-testing/net/wireless/lib80211.c: In function
> 'lib80211_crypt_info_init':
> /work/src/wireless-testing/net/wireless/lib80211.c:83: error: implicit
> declaration of function 'setup_timer'
> /work/src/wireless-testing/net/wireless/lib80211.c: In function
> 'lib80211_crypt_info_free':
> /work/src/wireless-testing/net/wireless/lib80211.c:95: error: implicit
> declaration of function 'del_timer_sync'
> /work/src/wireless-testing/net/wireless/lib80211.c: In function
> 'lib80211_crypt_deinit_handler':
> /work/src/wireless-testing/net/wireless/lib80211.c:157: error:
> implicit declaration of function 'add_timer'
> /work/src/wireless-testing/net/wireless/lib80211.c: In function
> 'lib80211_crypt_delayed_deinit':
> /work/src/wireless-testing/net/wireless/lib80211.c:182: error:
> implicit declaration of function 'timer_pending'
> make[3]: *** [net/wireless/lib80211.o] Error 1
> make[2]: *** [net/wireless] Error 2
> make[1]: *** [net] Error 2
> make: *** [sub-make] Error 2

Signed-off-by: Rami Rosen <ramirose@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>