iavf: Fix hang during reboot/shutdown

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

iavf: Fix hang during reboot/shutdown

Recent commit 974578017fc1 ("iavf: Add waiting so the port is

initialized in remove") adds a wait-loop at the beginning of

iavf_remove() to ensure that port initialization is finished

prior unregistering net device. This causes a regression

in reboot/shutdown scenario because in this case callback

iavf_shutdown() is called and this callback detaches the device,

makes it down if it is running and sets its state to __IAVF_REMOVE.

Later shutdown callback of associated PF driver (e.g. ice_shutdown)

is called. That callback calls among other things sriov_disable()

that calls indirectly iavf_remove() (see stack trace below).

As the adapter state is already __IAVF_REMOVE then the mentioned

loop is end-less and shutdown process hangs.

The patch fixes this by checking adapter's state at the beginning

of iavf_remove() and skips the rest of the function if the adapter

is already in remove state (shutdown is in progress).

Reproducer:

1. Create VF on PF driven by ice or i40e driver

2. Ensure that the VF is bound to iavf driver

3. Reboot

[52625.981294] sysrq: SysRq : Show Blocked State

[52625.988377] task:reboot state:D stack: 0 pid:17359 ppid: 1 f2

[52625.996732] Call Trace:

[52625.999187] __schedule+0x2d1/0x830

[52626.007400] schedule+0x35/0xa0

[52626.010545] schedule_hrtimeout_range_clock+0x83/0x100

[52626.020046] usleep_range+0x5b/0x80

[52626.023540] iavf_remove+0x63/0x5b0 [iavf]

[52626.027645] pci_device_remove+0x3b/0xc0

[52626.031572] device_release_driver_internal+0x103/0x1f0

[52626.036805] pci_stop_bus_device+0x72/0xa0

[52626.040904] pci_stop_and_remove_bus_device+0xe/0x20

[52626.045870] pci_iov_remove_virtfn+0xba/0x120

[52626.050232] sriov_disable+0x2f/0xe0

[52626.053813] ice_free_vfs+0x7c/0x340 [ice]

[52626.057946] ice_remove+0x220/0x240 [ice]

[52626.061967] ice_shutdown+0x16/0x50 [ice]

[52626.065987] pci_device_shutdown+0x34/0x60

[52626.070086] device_shutdown+0x165/0x1c5

[52626.074011] kernel_restart+0xe/0x30

[52626.077593] __do_sys_reboot+0x1d2/0x210

[52626.093815] do_syscall_64+0x5b/0x1a0

[52626.097483] entry_SYSCALL_64_after_hwframe+0x65/0xca