riscv64: [codegen] Implement VisitMin/VisitMax.

And use instructions from the "Zbb" extenstion to implement
the integer variants of Min/Max and improve the code emitted
for Ror.

Test: m test-art-host-gtest
Bug: 283082089
Change-Id: I809d53bfebf46a047536c79541802e74faaa287f
2 files changed