[IPVS]: Use IP_VS_WAIT_WHILE when encessary.

For architectures that don't have a volatile atomic_ts constructs like
while (atomic_read(&something)); might result in endless loops since a
barrier() is missing which forces the compiler to generate code that
actually reads memory contents.
Fix this in ipvs by using the IP_VS_WAIT_WHILE macro which resolves to
while (expr) { cpu_relax(); }
(why isn't this open coded btw?)

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ipvs/ip_vs_ctl.c

@@ -908,7 +908,7 @@ ip_vs_edit_dest(struct ip_vs_service *svc, struct ip_vs_dest_user *udest)
 	write_lock_bh(&__ip_vs_svc_lock);
 
 	/* Wait until all other svc users go away */
-	while (atomic_read(&svc->usecnt) > 1) {};
+	IP_VS_WAIT_WHILE(atomic_read(&svc->usecnt) > 1);
 
 	/* call the update_service, because server weight may be changed */
 	svc->scheduler->update_service(svc);