qed: Fix possible error in populating max_tc field.

Some adapters may not publish the max_tc value. Populate the default
value for max_tc field in case the mfw didn't provide one.

Signed-off-by: Sudarsana Reddy Kalluru <Sudarsana.Kalluru@cavium.com>
Signed-off-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>