vfio: blacklist loading of unstable roms

vfio: blacklist loading of unstable roms

Certain cards such as the Broadcom BCM57810 have rom quirks
that exhibit unstable system behavior duing device assignment. In
the particular case of 57810, rom execution hangs and if a FLR
follows, the device becomes inoperable until a power cycle. This
change blacklists loading of rom for such cards unless the user
specifies a romfile or rombar=1 on the cmd line

Signed-off-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>