icnss: Add fatal error string in icnss error message

Add unique signature in icnss fatal error message, which is used to
improve debugging as debug automation depends on this string.

CRs-Fixed: 2234375
Change-Id: Ie0c25f3bc543c507cecec3add68c2edd2f3abe8b
Signed-off-by: Yuanyuan Liu <yuanliu@codeaurora.org>