bonding: make release_and_destroy static

Only used in main file.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>