bonding: fix multiple module load problem

Some users still load bond module multiple times to create bonding
devices.  This accidentally was broken by a later patch about
the time sysfs was fixed.  According to Jay, it was broken
by:
   commit b8a9787e
   Author: Jay Vosburgh <fubar@us.ibm.com>
   Date:   Fri Jun 13 18:12:04 2008 -0700

     bonding: Allow setting max_bonds to zero

Note: sysfs and procfs still produce WARN() messages when this is done
so the sysfs method is the recommended API.
Signed-off-by: NStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: NJay Vosburgh <fubar@us.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_sysfs.c

@@ -1541,6 +1541,7 @@ int bond_create_sysfs(void)
 			printk(KERN_ERR
 			       "network device named %s already exists in sysfs",
 			       class_attr_bonding_masters.attr.name);
+		ret = 0;
 	}
 
 	return ret;