ethdev: fix close failure handling

ethdev: fix close failure handling

If a failure happens when closing a port,
it was unnecessarily failing again in the function eth_err(),
because of a check against HW removal cause.
Indeed there is a big chance the port is released at this point.
Given the port is in the middle (or at the end) of a close process,
checking the error cause by accessing the port is a non-sense.
The error check is replaced by a simple return in the close function.

Bugzilla ID: 624
Fixes: 8a5a0aad5d3e ("ethdev: allow close function to return an error")
Cc: stable@dpdk.org
Reported-by: Anatoly Burakov <anatoly.burakov@intel.com>
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
Tested-by: Anatoly Burakov <anatoly.burakov@intel.com>