nl80211: Reset split_start when netlink skb is exhausted

nl80211: Reset split_start when netlink skb is exhausted

commit f12cb2893069495726c21a4b0178705dacfecfe0 upstream.

When the netlink skb is exhausted split_start is left set. In the
subsequent retry, with a larger buffer, the dump is continued from the
failing point instead of from the beginning.

This was causing my rt28xx based USB dongle to now show up when
running "iw list" with an old iw version without split dump support.

Fixes: 3713b4e364ef ("nl80211: allow splitting wiphy information in dumps")
Signed-off-by: Pontus Fuchs <pontus.fuchs@gmail.com>
[avoid the entire workaround when state->split is set]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>