wifi: mac80211: Add multicast to unicast support for 802.3 path

wifi: mac80211: Add multicast to unicast support for 802.3 path

mac80211 already supports multicast-to-unicast conversion for
native 802.11 TX paths, but this handling is missing for the
802.3 transmit path. Due to that the packet never converted to
unicast and directly pass it to 802.11 Tx path by checking the
destination address as multicast.

Extend ieee80211_subif_start_xmit_8023() to honor the
multicast_to_unicast setting by cloning and converting multicast
Ethernet frames into per-station unicast transmissions, following
the same behavior of the native 802.11 TX path and allow it
to take 802.3 path.

Signed-off-by: Tamizh Chelvam Raja <tamizh.raja@oss.qualcomm.com>
Link: https://patch.msgid.link/20260604162403.1563729-3-tamizh.raja@oss.qualcomm.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>