Finish cleanup in kvm.c revisions 1.10 and 1.11 -- mark sf (swapfile)
argument to kvm_open() and kvm_openfiles() as unused.

BSD didn't read swap since kvm.c CSRG revision 5.21 (u-area is pageable
under new VM. no need to read from swap.)

The old !NEWVM code was removed in CSRG revision 5.23 (~ten years ago).