qcacld-3.0: Flush psoc idle work during WIFI on/off

Currently in the driver there is a possible race condition between
hdd_open and idle_psoc_timeout wherein stop modules is being done. Both
these operations can potentially occur in parallel.

To synchronize, flush the idle_psoc_work in wlan_hdd_state_ctrl_param_write
which is called during WiFi ON/OFF.

Change-Id: I1d53fa9d53ca31c2c1466f0ee809a07a86a06ee0
CRs-Fixed: 2701512