srcu: Add data_race() to ->srcu_lock_count and ->srcu_unlock_count arrays

The srcu_data structure's ->srcu_lock_count and ->srcu_unlock_count arrays
are read and written locklessly, so this commit adds the data_race()
to the diagnostic-print loads from these arrays in order mark them as
known and approved data-racy accesses.

This data race was reported by KCSAN. Not appropriate for backporting due
to failure being unlikely and due to this being used only by rcutorture.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>