wl12xx: 1281/1283 support - Add dummy packet support

Support sending dummy packet to wl128x FW as results of
dummy packet event. That is part of dynamic TX mem blocks mechanism.

Only send dummy packet when not in AP mode.

[Even though the DUMMY_PACKET_EVENT_ID and the
STA_REMOVE_COMPLETE_EVENT_ID events are defined to the same value, we
need to treat them separately in the code.  Keep the check and enable
STA_REMOVE_COMPLETE_EVENT_ID for AP mode and DUMMY_PACKET_EVENT_ID for
STA.  Moved one warning to a cleaner place.  Use WL1271_TID_MGMT for
dummy packets -- Luca]

Signed-off-by: Shahar Levi <shahar_levi@ti.com>
Reviewed-by: Luciano Coelho <coelho@ti.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>