nl80211: Fix link indexing in nl80211_connect_common()

nl80211: Fix link indexing in nl80211_connect_common()

In some places the wrong index variable was used to access the link
configuration. Fix this by simply using link_id instead of i.

With this, the i loop variable is not needed anymore. We can simply
always pass 0 to nla_nest_start(). Also, the kernel does not care about
the order that the links are provides, so just remove the special
handling for the association link.

Fixes: a2c4c0b1b6bb ("nl80211: Support MLD association request")
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>