arch-riscv,tests: Add insttests for RV64C

This patch adds instruction tests for the RV64C extension
implementation. It also updates existing executables for the latest
riscv-tools now that they are compatible.

[Update for changes to parents.]

Change-Id: Id4cfd966a8cae39b0d728b02849622fd00ee7e0e
Reviewed-on: https://gem5-review.googlesource.com/3862
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>