ath10k: fix num_sends_allowed replenishing

Commit e9bb0aa3 ("ath10k: delete struct ce_sendlist") broke
num_sends_allowed incrementing. num_sends_allowed
exceeded initial values and could overflow.

This code was supposed to replenish
num_sends_allowed for partial sendlist items (i.e.
before final sendlist item from a sendlist was
completed and could be processed by completion
handlers).

Fortunately it seems it did not cause any major breakage,
yet.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>