locking: locktorture: Do not include rwlock.h directly

Including rwlock.h directly will cause kernel builds to fail
if CONFIG_PREEMPT_RT is defined. The correct header file
(rwlock_rt.h OR rwlock.h) will be included by spinlock.h which
is included by locktorture.c anyway.

Remove the include of linux/rwlock.h.

Signed-off-by: Wolfgang M. Reimer <linuxball@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>