configs: Move riscv_fs.py to example/gem5_library

This commit also does some minor cleanup of the riscv_fs.py, as well as
renaming it `riscv-fs.py`.

Change-Id: I2ab5f7a3282d7eacf66a7d5b3609983d396b9218
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/51789
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
1 file changed