[PATCH 0/4] riscv: Add semihosting support [v10]

[Keith Packard]

This series first adapts the existing ARM semihosting code to be
architecture-neutral, then adds RISC-V semihosting support using that.

Patch 1/4 moves the ARM semihosting support code to common directories and
adapts the build system to match.

Patch 2/4 changes the public API to this code to use
architecture-independent names and types.

Patch 3/4 changes the internals of this code to use architecture
neutral types where practical, and adds helper functions to abstract
away the architecture-specific details.

Patch 4/4 adds the RISC-V support, including modifying the breakpoint
handling code to recognize a semihosting sequence and adding RISC-V
specific implementations of the helper functions.