ethdev: remove name from extended statistic fetch

The current extended ethernet statistics fetching involve doing several
string operations, which causes performance issues if there are lots of
statistics and/or network interfaces. This patch changes the test-pmd
and proc_info applications to use the new xstats API, and removes
deprecated code associated with the old API.

Signed-off-by: Remy Horton <remy.horton@intel.com>