bnx2x: Remove unused inline function bnx2x_vf_vlan_credit

commit 05cc5a39 ("bnx2x: add vlan filtering offload")
left behind this, remove it.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>