bnx2x: More Shutdown revisions

Submission d9aee591 "bnx2x: Don't release PCI bars on shutdown" separated
the PCI remove and shutdown flows, but pci_disable_device() is still
being called on both.
As a result, a dev_WARN_ONCE will be hit during shutdown for every bnx2x
VF probed on a hypervisor (as its shutdown callback will be called and later
pci_disable_sriov() will call its remove callback).

This calls the pci_disable_device() only on the remove flow.

Signed-off-by: Yuval Mintz <yuvalmin@broadcom.com>
Signed-off-by: Ariel Elior <ariele@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>