Documentation: lockstat: Fix typo lokcing -> locking

Cc: Jiri Kosina <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Signed-off-by: Stephen Boyd <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/locking/lockstat.txt

···
 - HOW
 
 Lockdep already has hooks in the lock functions and maps lock instances to
-lock classes. We build on that (see Documentation/lokcing/lockdep-design.txt).
+lock classes. We build on that (see Documentation/locking/lockdep-design.txt).
 The graph below shows the relation between the lock functions and the various
 hooks therein.