wifi: iwlwifi: mld: use cfg80211_chandef_get_width()

We can use this helper now to simplify some code.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250424153620.586e12d3d07c.Idc27c446d00a7f7925ee76b356f53b72dafc5745@changeid


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