arch,cpu: Get rid of unused/unimplemented vtophys variants.

arch,cpu: Get rid of unused/unimplemented vtophys variants.

The version of vtophys which didn't take a ThreadContext had only been
implemented on Alpha which has since been removed, so this version of
the function was completely unimplemented and never used.

This change also gets rid of the dbg_vtophys which was sometimes
implemented but also never used, and takes the opportunity to fix up
some style problems in some of the vtophys arch files.

Change-Id: Ie10f881f8ce08c7188e71805357cf3264be4c81a
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/26224
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>