UPSTREAM: virt_wifi: fix error return code in virt_wifi_newlink()

Fix to return a negative error code from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: c7cdba31ed8b ("mac80211-next: rtnetlink wifi simulation device")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
(cherry picked from commit f9d672f1c2ca36b788511bbd773d650c744e109a)
Change-Id: Ia6290ab996afca7b33e1a8e9b8bcfc0ecbe252f4
Signed-off-by: Cody Schuffelen <schuffelen@google.com>