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>

riscv: fix compatibility with Linux toolchain

Previously, RISC-V in gem5 only supported RISC-V's Newlib toolchain
(riscv64-unknown-elf-*) due to incorrect assumptions made in the initial
setup of the user stack in SE mode. This patch fixes that by referring
to the RISC-V proxy kernel code (https://github.com/riscv/riscv-pk) and
setting up the stack according to how it does it. Now binaries compiled
using the Linux toolchain (riscv64-unknown-linux-gnu-*) will run as
well.

[Update for recent changes to MemState to add accessors and mutators to
get its members.]

Change-Id: I6d2c486df7688efe3df54273e9aa0fd686851285
Reviewed-on: https://gem5-review.googlesource.com/2305
Maintainer: Alec Roelke <ar4jc@virginia.edu>
Reviewed-by: Brandon Potter <Brandon.Potter@amd.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

riscv: [Patch 8/5] Added some regression tests to RISC-V

This patch is the eighth patch in a series adding RISC-V to gem5, and
third of the bonus patches to the original series of five. It adds some
regression tests to RISC-V.

Regression tests included:
- se/00.hello
- se/02.insttest (split into several binaries which are not included due
to large size)

The tests added to 00.insttest will need to be build manually; to
facilitate this, a Makefile is included. The required toolchain and
compiler (riscv64-unknown-elf-gcc) can be built from the riscv-tools
GitHub repository at https://github.com/riscv/riscv-tools.

Note that because EBREAK only makes sense when gdb is running or while in
FS mode, it is not included in the linux-rv64i insttest. ERET is not
included because it does not make sense in SE mode and, in fact, causes
a panic by design.

Note also that not every system call is tested in linux-rv64i; of the ones
defined in linux/process.hh, some have been given numbers but not
definitions for the toolchain, or are merely stubs that always return 0. Of
the ones that do work properly, only a subset are tested due to similar
functionality.

Signed-off by: Alec Roelke

Signed-off by: Jason Lowe-Power <jason@lowepower.com>