idpf: implement pci error handlers

Add callbacks to handle PCI errors and FLR reset. When preparing to handle
reset on the bus, the driver must stop all operations that can lead to MMIO
access in order to prevent HW errors. To accomplish this, introduce helper
idpf_reset_prepare() that gets called prior to FLR or when PCI error is
detected. Upon resume the recovery is done through the existing reset path
by starting the event task.

The following callbacks are implemented:
.reset_prepare runs the first portion of the generic reset path leading up
to the part where we wait for the reset to complete.
.reset_done/resume runs the recovery part of the reset handling.
.error_detected is the callback dealing with PCI errors, similar to the
prepare call, we stop all operations, prior to attempting a recovery.
.slot_reset is the callback attempting to restore the device, provided a
PCI reset was initiated due to an error on the bus.

Whereas previously the init logic guaranteed netdevs during reset, the
addition of idpf_detach_and_close() to the PCI callbacks flow makes it
possible for the function to be called without netdevs. Add check to
avoid NULL pointer dereference in that case.

Co-developed-by: Alan Brady <alan.brady@intel.com>
Signed-off-by: Alan Brady <alan.brady@intel.com>
Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Reviewed-by: Jay Bhat <jay.bhat@intel.com>
Reviewed-by: Madhu Chittim <madhu.chittim@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>