[RISCV] Add missing patterns for rotr with immediate for Zbb/Zbp extensions.

DAGCombine doesn't canonicalize rotl/rotr with immediate so we
need patterns for both.

Remove the custom matcher for rotl to RORI and just use a SDNodeXForm
to convert the immediate instead. Doing this gives priority to the
rev32/rev16 versions of grevi over rori since an explicit immediate
is more precise than any immediate. I also added rotr patterns for
rev32/rev16. And removed the (or (shl), (shr)) patterns that should be
combined to rotl by DAG combine.

There is at least one other grev pattern that probably needs a
another rotr pattern, but we need more test coverage first.

Differential Revision: https://reviews.llvm.org/D90575