bhyve snapshot fix for AMD CPUs

[mihaiburcea15_gmail.com]

Summary

This patch fixes the AMD implementation for snapshotting.
It removes unnecessary vmcb fields that should not be saved and duplicates.

This patch was applied on top of 0630a06b2ab013ba6a877871eafde1889251ebdb.

Test Plan

The patch was tested on AMD Ryzen 1600 AF.
For testing, we started a virtual machine that executed an infinite loop and saved its state using bhyvectl --suspend=file.ckp --vm=guest_vm.
Then, we restored its state using bhyve ... -r file.ckp guest_vm.

More information about save and restore can be found at this link: https://github.com/FreeBSD-UPB/freebsd-src/wiki/Save-and-Restore-a-virtual-machine-using-bhyve