net/iavf: enable PCI bus master after reset

net/iavf: enable PCI bus master after reset

The VF reset can be triggered by the PF reset event, then the PCI bus
master will be cleared, the VF will be not allowed to issue any Memory
or I/O Requests.

So after the reset event is detected, always enable the PCI bus master.
And if failed, the device or system may be in an invalid state, so keep
the VF reset state to mark it as I/O error.

Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
Acked-by: Beilei Xing <beilei.xing@intel.com>