doc: Fix list: rcu_access_pointer() is not lockdep-checked

The rcu_access_pointer() macro does not consult lockdep by design because
it is intended to be used outside of RCU read-side critical sections.
This commit therefore makes a separate list for it in whatisRCU.rst.

Similarly, RCU_LOCKDEP_WARN(), rcu_sleep_check(), and RCU_NONIDLE()
do not do anything with pointer access.  This commit therefore creates
a separate utility-API list for them.
Signed-off-by: NPaul E. McKenney <paulmck@kernel.org>

Documentation/RCU/whatisRCU.rst

@@ -1057,14 +1057,20 @@ SRCU: Initialization/cleanup::
 	init_srcu_struct
 	cleanup_srcu_struct
 
-All: lockdep-checked RCU-protected pointer access::
+All: lockdep-checked RCU utility APIs::
 
-	rcu_access_pointer
-	rcu_dereference_raw
 	RCU_LOCKDEP_WARN
 	rcu_sleep_check
 	RCU_NONIDLE
 
+All: Unchecked RCU-protected pointer access::
+
+	rcu_dereference_raw
+
+All: Unchecked RCU-protected pointer access with dereferencing prohibited::
+
+	rcu_access_pointer
+
 See the comment headers in the source code (or the docbook generated
 from them) for more information.