Merge from projects/bhyve_svm all the changes outside vmm.ko or bhyve utilities:

Add support for AMD's nested page tables in pmap.c:

• Provide the correct bit mask for various bit fields in a PTE (e.g. valid bit) for a pmap of type PT_RVI.
• Add a function 'pmap_type_guest(pmap)' that returns TRUE if the pmap is of type PT_EPT or PT_RVI.

Add CPU_SET_ATOMIC_ACQ(num, cpuset):
This is used when activating a vcpu in the nested pmap. Using the 'acquire'
variant guarantees that the load of the 'pm_eptgen' will happen only after
the vcpu is activated in 'pm_active'.

Add defines for various AMD-specific MSRs.

Submitted by: Anish Gupta (akgupt3@gmail.com)