pub fn rounding_shift(val: S<32>, shamt: U<5>) -> S<32>
Rounding shift (round-to-nearest-even) https://github.com/ucb-bar/gemmini/blob/be2e9f26181658895ebc7ca7f7d6be6210f5cdef/src/main/scala/gemmini/Arithmetic.scala#L97C7-L97C22 https://github.com/riscv/riscv-v-spec/blob/master/v-spec.adoc#38-vector-fixed-point-rounding-mode-register-vxrm