icnss: Update event workqueue flags

There are events doing probe/remove operations that
shouldn't be swapped. Strict the order by setting
max_active to 1 and adding the WQ_UNBOUND flag.

Change-Id: If65c952622bbaa3f71de6d02c81dbbba5ccead4e
CRs-Fixed: 1046131
Signed-off-by: Yuanyuan Liu <yuanliu@codeaurora.org>