pci: propagate PMD removal error value for unplug
pci: propagate PMD removal error value for unplug

If a PCI device detach removal fails, returns the actual removal
operator error value.

Use this value within pci->unplug, as it may help applications solve an
issue with the feature or more accurately warn their users.

Signed-off-by: Gaetan Rivet <a6b9f1aecd7707f01344f211143eb3bcaeb0c5c3@6wind.com>
Acked-by: Thomas Monjalon <5f50a84c1fa3bcff146405017f36aec1a10a9e38@monjalon.net>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk