vfio/pci: Fallback huge faults for unaligned pfn

vfio/pci: Fallback huge faults for unaligned pfn

The PFN must also be aligned to the fault order to insert a huge
pfnmap.  Test the alignment and fallback when unaligned.

Fixes: f9e54c3a2f5b ("vfio/pci: implement huge_fault support")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=219619
Reported-by: Athul Krishna <athul.krishna.kr@protonmail.com>
Reported-by: Precific <precification@posteo.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Tested-by: Precific <precification@posteo.de>
Link: https://lore.kernel.org/r/20250102183416.1841878-1-alex.williamson@redhat.com
Cc: stable@vger.kernel.org
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>