mac80211: initialize return flags in HE 6 GHz operation parsing

mac80211: initialize return flags in HE 6 GHz operation parsing

Dan points out that if ieee80211_chandef_he_6ghz_oper() succeeds,
we don't initialize 'ret'. Initialize it to 0 in this case, since
everything went fine and nothing has to be disabled.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 6d6b20bf862e ("mac80211: determine chandef from HE 6 GHz operation")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://lore.kernel.org/r/20200603111500.bd2a5ff37b83.I2c3f338ce343b581db493eb9a0d988d1b626c8fb@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>