Move portable code in port out of superh for use in riscv

[JamesTimothyMeech]

Is your feature request related to a problem?
Currently the port directory for portable code is inside the superh directory.
I propose that we move it out from the superh directory such that the port code can be used for both the superh and riscv versions of sunflower.

Describe the solution you'd like
Move the port directory to the same level as the superh and riscv directories and fix all the examples that this move will break. Any superH specific code in the port directory will be moved to a file named superHspecific.c

Describe alternatives you've considered
This is the most clean solution. Referencing code in the superh directory from the riscv directory would be confusing and unclean.

Additional context
This is one of a pair of pull requests. The first one will move port and fix everything that is broken and the second one will implement the virtual sensor examples for riscv.