net: iwlegacy: remove unused variable

Fix:

drivers/net/wireless/iwlegacy/4965.c: In function ‘il4965_post_associate’:
drivers/net/wireless/iwlegacy/4965.c:1751:25: warning: variable ‘conf’ set but
not used [-Wunused-but-set-variable]

seen when building allmodconfig on x86_64 with W=1 by removing the unused
variable.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>