RISC-V: move various alias entries

For disassembly to only use spec-mandated aliases, respective non-alias
entries need to come ahead of their alias ones. Since identical
mnemonics need to stay together, whole groups are moved up where
necessary.

This partly reverts 839189bc ("RISC-V: re-arrange opcode table for
consistent alias handling"), but then also goes beyond a plain revert.

Reviewed-by: Tsukasa OI <research_trasio@irq.a4lg.com>
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>