riscv: KVM: Apply insn-def to hlv encodings

Introduce hlv instruction encodings and apply them to KVM's use.
We're careful not to introduce hlv.d to 32-bit builds. Indeed,
we ensure the build fails if someone tries to use it.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Anup Patel <anup@brainfault.org>