riscv: Implement benchmark log buffer

Can now perform benchmarks on the kernel using the log buffer to trace
kernel behavior.

Signed-off-by: Curtis Millar <curtis.millar@data61.csiro.au>

libsel4: fix license tags

These files should have been released under BSD-2-Clause in the first
place (as per parent LICENSE.md file).

Closes #245

Signed-off-by: Gerwin Klein <gerwin.klein@data61.csiro.au>

Enabled IPC debug features under new config

Introduced a new config flag to enable
userError format strings to be written to the IPC buffer.
Another config bool has been introduced to toggle
printing the error out and this can also be set at runtime.

Signed-off-by: Saer Debel <saer.debel@data61.csiro.au>

replacing all ifndef with pargma once

All the kernel header files now use pargma once rather than the ifndef,
as the pre-processed C files do not change while header files
are protected with pargma once. This will also solve any naming issues
caused by ifndef.

Convert license tags to SPDX identifiers

This commit also converts our own copyright headers to directly use
SPDX, but leaves all other copyright header intact, only adding the
SPDX ident. As far as possible this commit also merges multiple
Data61 copyright statements/headers into one for consistency.

trivial: Bugfix, use the correct config macro

Use the correct config macro to enable code injection.

mcs: libsel4 for RISC-V

This uses the aarch64 code as a basis for implementing the full set of
new and updated libsel4 functions for RISC-V.

Add syscall for setting the current TLS register.

Some platforms and configurations do not allow user code to change the
value of the register used for TLS. On these architectures a syscall can
be used to allow the kernel to update the register on their behalf.

This does not immediately update the value in the user context on many
configurations as the values are only stored in the user context on a
context switch.

Remove platform IPC buffer register.

This removes the assumption that each platform sotres the IPC buffer
address in a platform-specific register. The IPC buffer address is
instead stored in a thread-local variable in libsel4 which must be
initialised by the runtime.

style: set code width to 120

style: consistently attach return type

Add attach-return-type to astyle

style: consistently align pointer with name

Run astyle with align-pointer=name

style: correct parenthesis padding

Use astyle's unpad-paren to unpad all parentheses that are not included
by pad-header, pad-oper, and pad-comma.

[libsel4] fix building with LibSel4FunctionAttributes

Correct exported functions that were still defined as 'static inline' to
use LIBSEL4_INLINE_FUNC so that they can be controlled by
LibSel4FunctionAttributes.

This is important to other languages that want to bind to the libsel4
static library instead of using the inline C functions.

riscv: fix style

SELFOUR-1264: riscv: Missing brace

Adds missing brace in syscalls.h and restyle the code accordingly.

RISCV: Place TODOs in the source

[SELFOUR-1156] RISC-V Port

Experimental release that supports both RV32 and RV64