wlcore: initialize per-link FW freed blocks correctly

When a link is allocated, sometimes the "freed packets" counter in FW
is non zero, but we always assumed it is. This caused us to incorrectly
account FW allocated blocks in some cases.

When operating in AP mode, this bug caused some stations to never
come back from PSM.

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