app/testpmd: support multi-process

app/testpmd: support multi-process

This patch adds multi-process support for testpmd.
For example the following commands run two testpmd
processes:

 * the primary process:

./dpdk-testpmd --proc-type=auto -l 0-1 -- -i \
   --rxq=4 --txq=4 --num-procs=2 --proc-id=0

 * the secondary process:

./dpdk-testpmd --proc-type=auto -l 2-3 -- -i \
   --rxq=4 --txq=4 --num-procs=2 --proc-id=1

Signed-off-by: Min Hu (Connor) <humin29@huawei.com>
Signed-off-by: Lijun Ou <oulijun@huawei.com>
Signed-off-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
Acked-by: Xiaoyun Li <xiaoyun.li@intel.com>
Acked-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: Aman Deep Singh <aman.deep.singh@intel.com>