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.

Manually tag missing 3rd-party licenses

Two files were previously ignored in the license check.

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.

riscv: replace braced-groups with functions.

Braced groups in expressions like

int x = 0;
x = ({x++; x;});

aren't supported by the C parser (or ISO C), so we replace the SBI_CALL
macro with an equivalent function.

[SELFOUR-1156] RISC-V Port

Experimental release that supports both RV32 and RV64