rcutorture: Get rid of duplicate sched.h include

linux/sched.h is included twice in kernel/rcutorture.c - once is enough.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>