[RISCV] Add more rev32 and rev16 test cases using fshl/fshr intrinsics. NFC

fshl/fshr intrinsics turn into rotl/rotr ISD opcodes and we don't
have a complete set of patterns.

We pattern match rotl, but we have a custom match for rori that gets
priority. We don't pattern match rotr and we don't have patterns
or custom code for rori from rotr.