bnx2x: Enable Multi-Cos feature.

FW version 7.13.15 addresses the issue in Multi-cos implementation.
This patch re-enables the Multi-Cos support in the driver.

Fixes: d1f0b5dc ("bnx2x: Disable multi-cos feature.")
Signed-off-by: Sudarsana Reddy Kalluru <skalluru@marvell.com>
Signed-off-by: Ariel Elior <aelior@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>