[qca-nss-sfe] stop sync delay work to prevent race condition when unloading ecm

Stop sync delay work first in the beginning of unregister
so that this work would not run while unloading ecm.

Change-Id: I15e2c6772ffc59542ec875ab43e7579d502fef2b
Signed-off-by: Wayne Tan <quic_wtan@quicinc.com>
diff --git a/sfe_ipv4.h b/sfe_ipv4.h
index 524e564..49fd0ff 100644
--- a/sfe_ipv4.h
+++ b/sfe_ipv4.h
@@ -457,5 +457,6 @@
 
 void sfe_ipv4_exit(void);
 int sfe_ipv4_init(void);
+bool sfe_ipv4_cancel_delayed_work_sync(void);
 
 #endif /* __SFE_IPV4_H */