wifi: mac80211: fix min center freq offset tracing

[ Upstream commit 248e4776 ]

We need to set the correct trace variable, otherwise we're
overwriting something else instead and the right one that
we print later is not initialized.

Fixes: b6011960

 ("mac80211: handle channel frequency offset")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230504134511.828474-2-gregory.greenman@intel.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>