wifi: mac80211: add some support for RX OMI power saving

wifi: mac80211: add some support for RX OMI power saving

In order to save power, it can be desirable to change the
RX operating mode using OMI to reduce the bandwidth. As the
handshake must be done in the HTC+ field, it cannot be done
by mac80211 directly, so expose functions to the driver to
request and finalize the necessary updates.

Note that RX OMI really only changes what the peer (AP) will
transmit to us, but in order to use it to actually save some
power (by reducing the listen bandwidth) we also update rate
scaling and then the channel context's mindef accordingly.

The updates are split into two in order to sequence them
correctly, when reducing bandwidth first reduce the rate
scaling and thus TX, then send OMI, then reduce the listen
bandwidth (chandef); when increasing bandwidth this is the
other way around. This also requires tracking in different
variables which part is applicable already.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250101070249.2c1a1934bd73.I4e90fd503504e37f9eac5bdae62e3f07e7071275@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>