[stable] x86/atomic functions missing memory clobber

I noticed that backports of commit 69d927bba395 "x86/atomic: Fix smp_mb__{before,after}_atomic()" didn't touch atomic_or_long() (present in 3.16) or atomic_inc_short() (present in 4.9 and earlier).

These functions were only implemented on x86 and not actually used in- tree. But it's possible they are used by some out-of-tree module, and that commit removed compiler barriers for them.

Would it might make sense to either 1. Add the memory clobber to these functions, or 2. Delete them on the affected stable branches?

Ben.