qcacld-3.0: Check for target ready before sending wmi command

SAP stop is in progress when FW down event is received
from platform driver. Vdev_stop command is not sent to
firmware due to target ready check but same check is not
present for self peer_delete command. This results in
assert in firmware since vdev_stop command is not received
before self peer_delete command.

Fix is to check if target is ready before sending wmi
command.

Change-Id: I91fa6aaffe4f35b446a3c8748f168e83620bf4b0
CRs-Fixed: 2266786