rcu: Update RCU maintainership
rcu: Update RCU maintainership

Drop Dipankar Sarma at his request (https://lkml.org/lkml/2014/6/2/628),
add Josh Triplett based on long-term review, contributions, and
agreement to take on this role (https://lkml.org/lkml/2014/6/2/554).

Signed-off-by: Paul E. McKenney <1e0ce936bb9b355d257bf5790d2513c3f28be22b@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <c028c213ed5efcf30c3f4fc7361dbde0c893c5b7@joshtriplett.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs