eal: do not panic on CPU detection

eal: do not panic on CPU detection

There may be no way to gracefully recover, but the application
should be notified that a failure happened, rather than completely
aborting.  This allows the user to proceed with a "slow-path" type
solution.

After this change, the EAL CPU NUMA node resolution step can no longer
emit an rte_panic.  This aligns with the code in rte_eal_init, which
expects failures to return an error code.

Signed-off-by: Aaron Conole <aconole@redhat.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>