[lld][test][RISCV] Don't use incorrectly normalised arch string in riscv-attributes...

[lld][test][RISCV] Don't use incorrectly normalised arch string in riscv-attributes-place.s

Per the psABI, the arch string should be normalised to (amongest other
things) always include the full version of each extension in form
zfoo1p0. riscv-attributes-place.s didn't conform to this, which is not a
problem for the current parsing logic, but this behaviour would change
with a patch I'm about to propose.

This makes riscv-sttributes-place.s feature a valid arch string, and
maintains test coverage for this particular form of invalid arch string
by adding it to riscv-attributes.s.