eal: introduce thread init helper

eal: introduce thread init helper

Introduce a helper responsible for initialising the per thread context.
We can then have a unified context for EAL and non-EAL threads and
remove copy/paste'd OS-specific helpers.

Per EAL thread CPU affinity setting is separated from the thread init.
It is to accommodate with Windows EAL where CPU affinity is not set at
the moment.
Besides, having affinity set by the master lcore in FreeBSD and Linux
will make it possible to detect errors rather than panic in the child
thread. But the cleanup when such an event happens is left for later.

A side-effect of this patch is that control threads can now use
recursive locks (rte_gettid() was not called before).

Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>