vfio/pci: Init the count variable in collecting hot-reset devices

vfio/pci: Init the count variable in collecting hot-reset devices

The count variable is used without initialization, it results in mistakes
in the device counting and crashes the userspace if the get hot reset info
path is triggered.

Fixes: f6944d4a0b87 ("vfio/pci: Collect hot-reset devices to local buffer")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=219010
Reported-by: Žilvinas Žaltiena <zaltys@natrix.lt>
Cc: Beld Zhang <beldzhang@gmail.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20240710004150.319105-1-yi.l.liu@intel.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>