qcacmn: Drop beacon/probe frames posted on Scan Queue if queue is full

Drop beacon/probe frames before posting on Scan queue if the queue
already has too many beacon/probes to process.

Also add scheduler API to get the queue size given the module ID.

Change-Id: I9153c7e77e74377863774b68e8163839e992358d
CRs-Fixed: 2298584
5 files changed