qcacmn: Reset vdev id for 11d scan after vdev destroy

In regulatory component, currently, default vdev id for 11d scan is
not reset after last sta vdev delete.

When SAP is stopped/started after last sta destroy, above behavior can
lead to invocation of WMI command to start/stop 11d scan for destroyed
vdev. Sometimes, this leads to firmware assert.

To address this, reset vdev_id_for_11d_scan to INVALID_VDEV_ID (0xFF)
after the last sta vdev destroy.

Change-Id: Ic8abaf6ac680b22fa9218c058a34cbf3c3b5bf1f
CRs-Fixed: 2415462