igb: Add Function Level Reset to PF and VF

igb: Add Function Level Reset to PF and VF

The Intel 82576EB GbE Controller say that the Physical and Virtual
Functions support Function Level Reset. Add the capability to the PF
device model using device property "x-pcie-flr-init" which is "on" by
default and "off" for machines <= 8.1 to preserve compatibility.

The FLR capability of the VF model is defined according to the FLR
property of the PF, this to avoid adding an extra compatibility
property.

Cc: Sriram Yagnaraman <sriram.yagnaraman@est.tech>
Fixes: 3a977deebe6b ("Intrdocue igb device emulation")
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Tested-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>