nl80211: Don't accept interrupted dump responses

nl80211: Don't accept interrupted dump responses

Netlink dump message may be interrupted if an internal inconsistency is
detected in the kernel code. This can happen, e.g., if a Beacon frame
from the current AP is received while NL80211_CMD_GET_SCAN is used to
fetch scan results. Previously, such cases would end up not reporting an
error and that could result in processing partial data.

Modify this by detecting this special interruption case and converting
it to an error. For the NL80211_CMD_GET_SCAN, try again up to 10 times
to get the full response. For other commands (which are not yet known to
fail in similar manner frequently), report an error to the caller.

Signed-off-by: Jouni Malinen <j@w1.fi>