wifi: mac80211: refactor chanreq.ap setting

There are now three places setting up chanreq.ap which always
depends on the mode (EHT being used or not) and override flag.
Refactor that code into a common function with a comment, to
make that clearer.

Reviewed-by: Miriam Rachel Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20240506215543.5cd6a209e58a.I3be318959d9e2df5dccd2d0938c3d2fcc6688030@changeid


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