Fix ixl(4) compilation with PCI_IOV pre-r266974
stable/10 doesn't have the if_getdrvflags(9) KPI. Reference the field in the
structure directly instead if the __FreeBSD_version is < 1100022, so the
driver can be built with PCI_IOV support on stable/10, which lacks this KPI.
MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division