eal: fix thread naming on FreeBSD

eal: fix thread naming on FreeBSD

rte_thread_setname was a macro defined only for Linux.
The function rte_thread_setname() can now be used on FreeBSD
as well on Linux.
It is required to build librte_pdump.

The macro was 0 for old glibc. The function is now returning -1.
The related logs are decreased from error to debug level because
it is not an important failure, just a debug inconvenience.

Fixes: 278f945402c5 ("pdump: add new library for packet capture")

Signed-off-by: Thomas Monjalon <thomas.monjalon@6wind.com>
Acked-by: David Marchand <david.marchand@6wind.com>