riscv: Define explicit functions for registers

Replaces (read|write|set|clear)_csr macros with explicit functions. This provides a boundary
for verification to reason about the operation.

riscv: Remove todos

This have been converted to JIRA issues.

riscv: Place traps in text section

Ensures that the traps are in the text section, and not the boot section, allowing for
kernel memory to be safely reused.

riscv: remove dev_pregs

We don't have any devices currently, and in future they will be
discovered, not statically specified.

riscv: remove cryptic printout

riscv: Parse the FDT during platform initialization

riscv: Remove dtb region from free memory

The DTB output should be preserved both during kernel bootup and ultimately given to the
rootserver. As such we should make sure to not include it as free memory.

riscv: Move `init_plat`

The platform should not be initialized till after the cpu has been.

riscv: Provide dtb region to try_init_kernel

Now that there is a different kernel window we can talk about the physical address of the
dtb and read it through the kernel window to determine it's size. Currently we just pass
the region to try_init_kernel, which does not yet do anything with it.

riscv: Remove smp boot code

The SMP code is incomplete and is confusing to have broken code around.

riscv: Redesign kernel window

Restructures the kernel window so that instead of being a single contiguous region with
a single offset to physical memory, it is two such regions. This allows us to use the
larger of the two windows as a window into physical memory, and the second smaller window
as a place to run the kernel image from. Having this additional window allows us to
link the kernel for different physical addresses without needing to change its virtual
address, or change the layout of the kernel window.
There are other ways to achieve this, but this is one of the simplest and matches how
x86-64 implements its kernel window.

riscv: remove capFTMapType

it is not used on riscv

riscv: Declare extern in global scope

Prevents a compiler warning

riscv: Valid c99 function definitions

riscv: Remove dead definitions

riscv: Remove broken dtb usage

The dtb output is not available after we have switched to our own kernel window and since
the platform should be moved till after the cpu has been initialized we remove the dtb
usage for now until the kernel window can be fixed such that we can access the dtb

RISC-V: Port FDT from riscv-pk (priv-1.10)

RISCV: Place TODOs in the source

[SELFOUR-1156] RISC-V Port

Experimental release that supports both RV32 and RV64