wlcore: increase number of BA sessions to 3

With the new FW (sigle role X.3.8.0.108, multi role X.5.4.0.21)
we are supporting 3 RX BA sessions, this change is to support this
new ability.

Signed-off-by: Assaf Azulay <assaf@ti.com>
Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>