wifi: mac80211: support returning the S1G short beacon skb

wifi: mac80211: support returning the S1G short beacon skb

When short beaconing is enabled, check the value of the sb_count
to determine whether we are to send a long beacon or short beacon.
sb_count represents the number of short beacons until the next
long beacon, where if its value is 0 we are to send a long beacon.
The value is then reset to the long beacon period, which represents
the number of beacon intervals between each long beacon. The decrement
process follows the same cadence as the decrement of the DTIM count value.

Signed-off-by: Lachlan Hodges <lachlan.hodges@morsemicro.com>
Link: https://patch.msgid.link/20250717074205.312577-5-lachlan.hodges@morsemicro.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>