x86: Implement translateFunctional.

x86: Implement translateFunctional.

This function is based off of vtophys in the full system case, and off
of the page table fill mechanism used in SE mode. It ignores what's
already in the TLB, and also ignores protection mechanisms.

This may need to be reworked in the future if, for instance, pages
still resident in the TLB but not in the page tables need to be
considered, but it should work at least for the time being.

Change-Id: If21701ca36a30805f4199312933a8afc91f20501
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/26405
Reviewed-by: Matthew Poremba <matthew.poremba@amd.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>