refscale: Exercise DEFINE_STATIC_SRCU_FAST() and init_srcu_struct_fast()

refscale: Exercise DEFINE_STATIC_SRCU_FAST() and init_srcu_struct_fast()

This commit updates the initialization for the "srcu-fast" scale
type to use DEFINE_STATIC_SRCU_FAST() when reader_flavor is equal to
SRCU_READ_FLAVOR_FAST.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: <bpf@vger.kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>