[RISCV] Increase complexity of RVV element extraction patterns

Somehow some tests failed in our downstream because it matched
VFMV+FSD pattern first. Both FSD and VSE patterns have the same
complexity, while FSD is matched before VSE in the generated
matcher table.

This problem only occurs in our downstream (so sorry that I can't
provide a test here) and increasing the value of `AddedComplexity`
can fix it.

Reviewed By: StephenFan, craig.topper

Differential Revision: https://reviews.llvm.org/D129360