LinuxKPI: Add compiler barriers to list_for_each_entry_lockless macro

[wulf]

Summary

so this list-traversal primitive may safely run concurrently with
the _rcu list-mutation primitives such as list_add_rcu()
as long as the traversal is guarded by rcu_read_lock().

Do it with reusing of list_for_each_entry_rcu macro which
does the same. On Linux it implements some additional
lockdep stuff which we skip.

Also move the macro to linux/rculist.h where it resides on Linux.

[• hselasky]

The commit message has some spelling errors - can you fix?

[wulf]

In D30795#692443, @hselasky wrote:

The commit message has some spelling errors - can you fix?

Did it with copy-paste from Linux header

[• hselasky]

Spelling:

Do it with reusing of list_for_each_entry_rcu macro which
does the same. On Linux it implements some additional
lockdep stuff which we skip.

Corrected:

Do it by reusing the "list_for_each_entry_rcu" macro which
does the same. On Linux it implements some additional
lockdep stuff which we skip.

[wulf]

Thank you! I replaced my spelling with yours in my local git repo.