cfg80211: Do not warn on same channel at the end of CSA

When cfg80211_update_assoc_bss_entry() is called, there is a
verification that the BSS channel actually changed. As some APs use
CSA also for bandwidth changes, this would result with a kernel
warning.

Fix this by removing the WARN_ON().

Signed-off-by: Ilan Peer <ilan.peer@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200326150855.96316ada0e8d.I6710376b1b4257e5f4712fc7ab16e2b638d512aa@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>