icnss: Send fw_down uevent during smp2p error handling

Subsys notifier chain for modem taking too long, MODEM SSR is
blocked, mutex held by wlan which is also in waiting state,
for event completion in wait_for_event_completion() routine.
To Avoid the above senario platform driver needs to send FW_DOWN
uevent during defered smp2p error handling as part of FW down event
wlan host completes the wait for completion events and release
the acquired lock.

CRs-Fixed: 2312089
Change-Id: I98b5c944328ab445f6dc112433bcd21c1f4e0773
Signed-off-by: Anurag Chouhan <achouhan@codeaurora.org>