app/testpmd: remove most uses of internal ethdev array

app/testpmd: remove most uses of internal ethdev array

This patch removes most uses of the global variable rte_eth_devices
from testpmd. This was done to avoid using the object directly which
applications should not do.

Most uses have been replaced with standard function calls, however
the use of it in the show_macs function could not be replaced as no
function call exists to get all mac addresses of a given port.

Signed-off-by: Paulis Gributs <paulis.gributs@intel.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: Xiaoyun Li <xiaoyun.li@intel.com>