[RISCV] Don't add -unaligned-scalar-mem to target features by default.

[craig.topper]

Summary

Only pass it +unaligned-scalar-mem/-unaligned-scalar-mem if the
user has passed one of the alignment options.

This allows us to add unaligned-scalar-mem as a feature on CPUs
that support it.

[wangpc]

llvm/lib/Target/RISCV/RISCVProcessors.td

185 ↗

(On Diff #554511)

This can be tested in clang/test/Driver/riscv-cpus.c.

[craig.topper]

llvm/lib/Target/RISCV/RISCVProcessors.td

185 ↗

(On Diff #554511)

This shouldn’t be in here. That was for testing and I accidentally committed it

[wangpc]

llvm/lib/Target/RISCV/RISCVProcessors.td

185 ↗

(On Diff #554511)

Are there any processors in upstream that support unaligned memory access so that we can test it?

[craig.topper]

Remove change to sifive-x280.

[wangpc]

LGTM.