msm: mdm: Ignore modem crashes during image upgrade.

When a modem image upgrade is in progress we now ignore any other
crash notifications that may come from other modems. These could
trigger an SSR and cause the upgrade to fail as well.

Change-Id: If96139c5106053ce6c8db05865f7d2fd9a503f23
Signed-off-by: Ameya Thakur <ameyat@codeaurora.org>