bnx2x: Do not enable CL37 BAM unless it is explicitly enabled

Enabling CL37 BAM on BCM8073 by default may lead to link issues since
not all switches support it. So enable CL37 BAM only if explicitly
selected.

Signed-off-by: Yaniv Rosner <yanivr@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>