[PATCH v3] RISC-V: Fix build with GCC-8

[Mark Zhuang]

Hi Jan, Maciej,

I redid some testing, and this build error reproduces with both gcc-9.4.0
and gcc-10.5.0; in both cases it is fixed by this patch.

Please feel free to adjust the commit message as needed when committing,
as well as the break/continue placement discussed earlier.

Thanks a lot,
Mark