rcu: Fix rcu_torture_read ftrace event

rcu: Fix rcu_torture_read ftrace event

commit d18a04157fc171fd48075e3dc96471bd3b87f0dd upstream.

Fix the rcutorturename field so that its size is correctly reported in
the text format embedded in trace.dat files. As it stands, it is
reported as being of size 1:

    field:char rcutorturename[8];   offset:8;       size:1; signed:0;

Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>
Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com>
Cc: stable@vger.kernel.org
Fixes: 04ae87a52074e ("ftrace: Rework event_create_dir()")
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
[ boqun: Add "Cc" and "Fixes" tags per Steven ]
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>