icnss: Add check for rejuvenate in fw_down

Currently, fw_down is not getting set in case of rejuvenate
since the qmi server never exit or arrive in case of rejuvenate.
Add ICNSS_REJUVENATE flag to take care of rejuvenate.

Change-Id: If85e8048cbad9a15e1c94af1c8d0012e004e6150
Signed-off-by: Anurag Chouhan <achouhan@codeaurora.org>