wl12xx: fix Tx security sequence number handling

Do not reset the security sequence number when issuing a join command or
interface is removed. Instead, reset the counter only during the unjoin
command.

Added the notion of counter wrap-around to the LSB number in
wl1271_tx_complete_packet.

Added post recovery padding to adjust for potential security number
progress during the recovery process by the firmware and avoid
potential interop issues in encrypted networks.

Signed-off-by: Oz Krakowski <ozk@ti.com>
Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>