qcacld-3.0: Fix tx queue is paused forever

Put flow control setting in the flow_pool_lock, which can avoid
race condition between ol_tx_desc_free and ol_tx_desc_alloc.
This is a refine based on Ib60139fd94a4fb88c92a7f8aaf886ae9d3ca4c75.

Change-Id: I8d89323b5631039d7ff5a141775cc5825389c18b
CRs-Fixed: 2297190
1 file changed