rcutorture: Add tracing-enabled version of TREE08

The TREE08 Kconfig fragment does not enable tracing, which is appropriate
for its test case.  However, this can be inconvenient in cases where
TREE08 locates RCU bugs.  This commit therefore adds a TREE08-T that
differs from TREE08 only in enabling CONFIG_RCU_TRACE.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Greg KH <gregkh@linuxfoundation.org>