net: bonding: Fix transmit load balancing in balance-alb mode

balance-alb mode used to have transmit dynamic load balancing feature
enabled by default.  However, transmit dynamic load balancing no longer
works in balance-alb after commit 8b426dc5 ("bonding: remove
hardcoded value").

Both balance-tlb and balance-alb use the function bond_do_alb_xmit() to
send packets.  This function uses the parameter tlb_dynamic_lb.
tlb_dynamic_lb used to have the default value of 1 for balance-alb, but
now the value is set to 0 except in balance-tlb.

Re-enable transmit dyanmic load balancing by initializing tlb_dynamic_lb
for balance-alb similar to balance-tlb.

Fixes: 8b426dc5 ("bonding: remove hardcoded value")
Signed-off-by: Kosuke Tatsukawa <tatsu@ab.jp.nec.com>
Acked-by: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: David S. Miller <davem@davemloft.net>