[llvm] [GISel][AArch64][RISCV] Don't call markAllIdxsAsCovered from minScalarSameAs/maxScalarSameAs. (PR #115637)

[Sam Elliott via llvm-commits]

https://github.com/lenary approved this pull request.

LGTM. I think there are other places which have the same issue in `LegalizerInfo.h`, but this is a good start.

https://github.com/llvm/llvm-project/pull/115637