[PATCH] Remove dead kill_sl prototype from sched.h

The kill_sl function doesn't exist in the kernel so a prototype is completely
unnecessary.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>