vfio-pci: Test device reset capabilities

vfio-pci: Test device reset capabilities

Not all resets are created equal.  PM reset is not very reliable,
especially for GPUs, so we might want to opt for a bus reset if a
standard reset will only do a D3hot->D0 transition.  We can also
use this to tell if the standard reset will do a bus reset (if
neither has_pm_reset or has_flr is probed, but the device still
supports reset).

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