esoc: Wait for modem status to go low in crash shutdown

Wait for modem status to go low in crash shutdown. This helps
cover the race condition where there is a crash during graceful
shutdown and we end up in crash path and send crash notification
to clients even before the modem status has gone low. Also set
the crash flag in interrupt path to avoid double queueing of ssr
work.

Change-Id: I680b79c7a1de5e44cb9fcfa0f9d67517c0398f62
Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>