documentation: RCU-protected array indexes no longer supported

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --cc Documentation/RCU/arrayRCU.txt
Simple merge

diff --cc Documentation/RCU/lockdep.txt
Simple merge

diff --cc Documentation/RCU/rcu_dereference.txt
Simple merge

diff --cc Documentation/RCU/whatisRCU.txt
Simple merge