bnx2x: Remove Comparison to bool in bnx2x_dcb.c

Fix the following coccicheck warning:

drivers/net/ethernet/broadcom/bnx2x/bnx2x_dcb.c:1548:17-31: WARNING:
Comparison to bool
drivers/net/ethernet/broadcom/bnx2x/bnx2x_dcb.c:1148:16-24: WARNING:
Comparison to bool
drivers/net/ethernet/broadcom/bnx2x/bnx2x_dcb.c:1158:30-38: WARNING:
Comparison to bool

Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>