ovs-numa: Remove non-linux stubs.

ovs-numa: Remove non-linux stubs.

Instead of having static inline stubs for non linux platform we can use
the implementations in ovs-numa.c.  With one small change to
ovs_numa_dump_cores_on_numa(), they will behave exactly like the
stubs for the non-linux case, because 'found_numa_and_core' will be
false and the socket and cpu hmaps will be empty.

There are a few places where conditional compilation is required: the
code that parses the linux specific sysfs entries and its dependencies.
It requires opendir() and readdir() and doesn't make sense outside of
linux anyway.

This change is required to have a cross-platform ovs-numa dummy
implementation for testing.

Signed-off-by: Daniele Di Proietto <diproiettod@vmware.com>
Acked-by: Ilya Maximets <i.maximets@samsung.com>