documentation: Add atomic_long_t to atomic_ops.txt
documentation: Add atomic_long_t to atomic_ops.txt

Signed-off-by: Paul E. McKenney <1e0ce936bb9b355d257bf5790d2513c3f28be22b@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <99f39d96f0d0b011d351b608fe7e2870596fa4a9@gmail.com>

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