Fix: Rename RISC-V machine scratch CSR #2949

Job	Run time
build-msvc (meson, windows-2022)	1m 13s
build-macos (macos-13)	36s
build-linux (jammy, 96b_carbon)	41s
build-macos (macos-14)	25s
build-mingw (windows-2022, mingw64)	1m 41s
build-linux (jammy, blackpill-f401cc)	36s
build-macos (macos-latest)	21s
build-mingw (windows-2022, ucrt64)	1m 42s
build-linux (jammy, blackpill-f401ce)	33s
build-macos (macos-13, gcc@11)	1m 9s
build-mingw (windows-2022, clang64)	1m 40s
build-linux (jammy, blackpill-f411ce)	37s
build-macos (macos-13, gcc@12)	1m 11s
build-linux (jammy, bluepill)	1m 1s
size-diff	40s
build-macos (macos-13, gcc@13)	1m 25s
build-linux (jammy, ctxlink)	35s
build-macos (macos-13, gcc@14)	1m 2s
build-linux (jammy, f072)	55s
build-macos (macos-14, gcc@11)	42s
build-linux (jammy, f3)	52s
build-macos (macos-14, gcc@12)	51s
build-linux (jammy, f4discovery)	32s
build-macos (macos-14, gcc@13)	51s
build-linux (jammy, hydrabus)	48s
build-macos (macos-14, gcc@14)	48s
build-linux (jammy, launchpad-icdi)	39s
build-linux (jammy, native)	32s
build-linux (jammy, native-uncommon)	39s
build-linux (jammy, native-st-clones)	32s
build-linux (jammy, native-riscv)	50s
build-linux (jammy, native-remote)	36s
build-linux (jammy, stlink)	33s
build-linux (jammy, stlinkv3)	36s
build-linux (jammy, swlink)	33s
	28m 57s

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