igb: Do not bring the device up after non-fatal error

In the Linux kernel, the following vulnerability has been resolved:

igb: Do not bring the device up after non-fatal error

Commit 004d25060c78 ("igb: Fix igb_down hung on surprise removal")
changed igb_io_error_detected() to ignore non-fatal pcie errors in order
to avoid hung task that can happen when igb_down() is called multiple
times. This caused an issue when processing transient non-fatal errors.
igb_io_resume(), which is called after igb_io_error_detected(), assumes
that device is brought down by igb_io_error_detected() if the interface
is up. This resulted in panic with stacktrace below.

[ T3256] igb 0000:09:00.0 haeth0: igb: haeth0 NIC Link is Down
[ T292] pcieport 0000:00:1c.5: AER: Uncorrected (Non-Fatal) error received: 0000:09:00.0
[ T292] igb 0000:09:00.0: PCIe Bus Error: severity=Uncorrected (Non-Fatal), type=Transaction Layer, (Requester ID)
[ T292] igb 0000:09:00.0: device [8086:1537] error status/mask=00004000/00000000
[ T292] igb 0000:09:00.0: [14] CmpltTO [ 200.105524,009][ T292] igb 0000:09:00.0: AER: TLP Header: 00000000 00000000 00000000 00000000
[ T292] pcieport 0000:00:1c.5: AER: broadcast error_detected message
[ T292] igb 0000:09:00.0: Non-correctable non-fatal error reported.
[ T292] pcieport 0000:00:1c.5: AER: broadcast mmio_enabled message
[ T292] pcieport 0000:00:1c.5: AER: broadcast resume message
[ T292] ------------[ cut here ]------------
[ T292] kernel BUG at net/core/dev.c:6539!
[ T292] invalid opcode: 0000 [#1] PREEMPT SMP
[ T292] RIP: 0010:napi_enable+0x37/0x40
[ T292] Call Trace:
[ T292] <TASK>
[ T292] ? die+0x33/0x90
[ T292] ? do_trap+0xdc/0x110
[ T292] ? napi_enable+0x37/0x40
[ T292] ? do_error_trap+0x70/0xb0
[ T292] ? napi_enable+0x37/0x40
[ T292] ? napi_enable+0x37/0x40
[ T292] ? exc_invalid_op+0x4e/0x70
[ T292] ? napi_enable+0x37/0x40
[ T292] ? asm_exc_invalid_op+0x16/0x20
[ T292] ? napi_enable+0x37/0x40
[ T292] igb_up+0x41/0x150
[ T292] igb_io_resume+0x25/0x70
[ T292] report_resume+0x54/0x70
[ T292] ? report_frozen_detected+0x20/0x20
[ T292] pci_walk_bus+0x6c/0x90
[ T292] ? aer_print_port_info+0xa0/0xa0
[ T292] pcie_do_recovery+0x22f/0x380
[ T292] aer_process_err_devices+0x110/0x160
[ T292] aer_isr+0x1c1/0x1e0
[ T292] ? disable_irq_nosync+0x10/0x10
[ T292] irq_thread_fn+0x1a/0x60
[ T292] irq_thread+0xe3/0x1a0
[ T292] ? irq_set_affinity_notifier+0x120/0x120
[ T292] ? irq_affinity_notify+0x100/0x100
[ T292] kthread+0xe2/0x110
[ T292] ? kthread_complete_and_exit+0x20/0x20
[ T292] ret_from_fork+0x2d/0x50
[ T292] ? kthread_complete_and_exit+0x20/0x20
[ T292] ret_from_fork_asm+0x11/0x20
[ T292] </TASK>

To fix this issue igb_io_resume() checks if the interface is running and
the device is not down this means igb_io_error_detected() did not bring
the device down and there is no need to bring it up.