[PATCH] bonding: Remove unneeded NULL test

Remove unneeded test for NULL.  Reported by Thomas Dillig
<tdillig@stanford.edu> and Isil Dillig <isil@stanford.edu> via Stephen
Hemminger <shemminger@osdl.org>.

Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>