riscv: Move all duplicate insn parsing macros into asm/insn.h

riscv: Move all duplicate insn parsing macros into asm/insn.h

kernel/traps_misaligned.c and kvm/vcpu_insn.c define the same macros to
extract information from the instructions.

Let's move the definitions into asm/insn.h to avoid this duplication.

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Clément Léger <cleger@rivosinc.com>
Link: https://lore.kernel.org/r/20250620-dev-alex-insn_duplicate_v5_manual-v5-3-d865dc9ad180@rivosinc.com
[pjw@kernel.org: updated to apply]
Signed-off-by: Paul Walmsley <pjw@kernel.org>