wifi: mac80211: expose ieee80211_chan_width_to_rx_bw() to drivers

Drivers might need to also do this calculation, no point in
them duplicating the code. Since it's so simple, just make
it an inline.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20241007144851.af003cb4a088.I8b5d29504b726caae24af6013c65b3daebe842a2@changeid


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