doc: update port hotplug in testpmd guide
doc: update port hotplug in testpmd guide

Signed-off-by: Bernard Iremonger <233eeff376ad0c06f66f06c5522ea3c4feb30d3b@intel.com>
Acked-by: Tetsuya Mukawa <b347a9f5840345582b30d055e1e99ac6ac7bce3c@igel.co.jp>

venkynv/dpdk-mirror,john-mcnamara-intel/dpdk,msune/dpdk,mixja/dpdk,msune/dpdk,mixja/dpdk,msune/dpdk,tsphillips/dpdk-fork,venkynv/dpdk-mirror,venkynv/dpdk-mirror,tsphillips/dpdk-fork,mixja/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,msune/dpdk,mixja/dpdk,john-mcnamara-intel/dpdk,venkynv/dpdk-mirror,tsphillips/dpdk-fork,tsphillips/dpdk-fork