vmm: Move local variables into ioctl handlers

[markj]

Summary

Make the ioctl handlers easy to read by moving local variables into
per-ioctl blocks. No functional change intended.

[emaste]

sys/amd64/vmm/vmm_dev_machdep.c

219

As an aside I wonder if it's reasonable to remove COMPAT_FREEBSD13 in the near future. I don't think we need to maintain backwards compat indefinitely for integrated system utilities.

263–265

I wonder if style(9) would permit

struct vm_pptdev_msi *pptmsi = (struct vm_pptdev_msi *)data;
error = ppt_setup_msi(vm, pptmsi->bus, pptmsi->slot,
    pptmsi->func, pptmsi->addr, pptmsi->msg, pptmsi->numvec);

[markj]

sys/amd64/vmm/vmm_dev_machdep.c

219

Yes, probably not. Or at least we could have a sysctl which lets one opt in there, with the default being opt-out.

It's kind of hard to weigh the usefulness of backwards compat in one subsystem vs. another. Device ioctls are less important than syscalls for sure. So I'm thinking such a sysctl should be per-subsystem rather than having a blanket "enable all compat 13 code" sysctl.

263–265

I guess that'd be fine. I just kept the existing style, I'm old-fashioned and don't really like combined declaration and initialization.