qcacmn: fix tx desc allocate from freed pool issue

The avail_desc is not set to 0 when the tx desc pool is
freed, later if still try to allocate tx desc by judgement
of avail_desc, panic happens.

Change-Id: Ia4565da1caa6898c6d4293e2658cf4ccf89563fa
CRs-Fixed: 2246328
2 files changed