YJIT: Avoid reloading InsnOut operands

[k0kubun]

There's this idiom in codegen.rs:

let object_reg = match object {
    Opnd::Reg(_) => object,
    _ => asm.load(object),
};

but Opnd::Reg doesn't seem to be really used in those places. When an argument operand is loaded into a register with asm.load, it's actually Opnd::InsnOut. So this PR fixes the condition to use Opnd::InsnOut instead.

I noticed this when I looked at generated code that contained an identical move mov rax, rax on expandarray. This PR removes such instructions.