eal: fix multi-process hotplug if already probed

eal: fix multi-process hotplug if already probed

When primary process receives an IPC attach request
of a device that's already locally-attached, it
doesn't setup its variables properly and is prone to
segfaulting on a subsequent rollback.

`ret = local_dev_probe(req->devargs, &dev)`

The above function will set `dev` pointer to the
proper device *unless* it returns with error. One of
those errors is -EEXIST, which the hotplug function
explicitly ignores. For -EEXIST, it proceeds with
attaching the device and expects the dev pointer to
be valid.

This patch makes `local_dev_probe` set the dev pointer
even if it returns -EEXIST.

Fixes: ac9e4a17370f ("eal: support attach/detach shared device from secondary")

Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>