[llvm] [RISCV][NFC] Allow SchedVar to be a def inside our scheduler model files. (PR #82634)

[Michael Maitland via llvm-commits]

michaelmaitland wrote:

We can move the predicate out, that is unrelated to this patch. We still need to def the SchedVar, otherwise it wont be able to find the SchedReadWrite that was defined just a few lines above.

https://github.com/llvm/llvm-project/pull/82634