ath10k: fix the logic of limiting tdls peer counts

The original idea is to limit the maximum TDLS peer link, but the logic
is always false, and never be able to restrict the number of TDLS peer
creation.

Fix the logic here and also move the checking earlier, so that it could
avoid to handle the failure case, e.g disable the tdls peer, delete the
peer and also vdev count cleanup.

Signed-off-by: Ryan Hsu <ryanhsu@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>