rcu: Remove CONFIG_SRCU

Now that all references to CONFIG_SRCU have been removed, it is time to
remove CONFIG_SRCU itself.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Petr Mladek <pmladek@suse.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>

kernel/rcu/Kconfig

@@ -53,9 +53,6 @@ config RCU_EXPERT
 
 	  Say N if you are unsure.
 
-config SRCU
-	def_bool y
-
 config TINY_SRCU
 	bool
 	default y if TINY_RCU

tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt

@@ -71,9 +71,5 @@ CONFIG_TASKS_RCU
 
 	These are controlled by CONFIG_PREEMPT and/or CONFIG_SMP.
 
-CONFIG_SRCU
-
-	Selected by CONFIG_RCU_TORTURE_TEST, so cannot disable.
-
 
 boot parameters ignored: TBD