drivers: esoc: Set crash status after modem status goes low

In situations where graceful shutdown and errfatal occur parallely on
modem, the graceful shutdown thread can go into crash shutdown path
because the crash flag is set asynchronously in mdm_errfatal handler.
In this case clients are notified that modem has crashed even though
it hasn't crashed completely. Clients perform cleanup based on the
assumption that modem is completely crashed and this might lead use
after free scenarios. Therefore wait for modem status to go low to
set the crash flag.

Change-Id: Ibafc54b3a136816c33476a28492bd081b053eecc
Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>