rcu: Annotate struct kvfree_rcu_bulk_data with __counted_by()

rcu: Annotate struct kvfree_rcu_bulk_data with __counted_by()

Add the __counted_by compiler attribute to the flexible array member
records to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
CONFIG_FORTIFY_SOURCE.

Increment nr_records before adding a new pointer to the records array.

Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
Reviewed-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Reviewed-by: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>