bhyve: Pass a vCPU ID of 0 to vm_setup_pptdev_msi*.

These ioctls are not vCPU-specific and the ioctl now ignores the vCPU
ID. 0 is used instead of -1 to provide limited forwards
compatibility.

Reviewed by: corvink, markj
Differential Revision: https://reviews.freebsd.org/D37651