Declare virtiovf_pci_aer_reset_done() as a static function to prevent
the below build warning.

"warning: no previous prototype for 'virtiovf_pci_aer_reset_done'
[-Wmissing-prototypes]"

Fixes: eb61eca0 ("vfio/virtio: Introduce a vfio driver over virtio devices")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Closes: https://lore.kernel.org/lkml/20231220143122.63337669@canb.auug.org.au/Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Link: https://lore.kernel.org/r/20231220082456.241973-1-yishaih@nvidia.comReported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202312202115.oDmvN1VE-lkp@intel.com/Signed-off-by: Alex Williamson <alex.williamson@redhat.com>