fastmodel: Update to c++14, and add some missing consts.
During the review for the CortexR52 model, a comment pointed out where
two consts can be added. Also we switched gem5 over to c++14, but the
project files for these other wrappers were still set to c++11.
Change-Id: I5fecdc896b0290deadcd0f55ea1dfe3806a98177
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/35857
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>