`ArmModeInstruction::DataProcessing` has redundancy in the fields

[AlessioC31]

pub enum ArmModeInstruction {
    DataProcessing {
        condition: Condition,
        alu_instruction: ArmModeAluInstruction,
        set_conditions: bool,
        op_kind: OperandKind,
        rn: u32,
        destination: u32,
        op2: AluSecondOperandInfo,
    },
...

We can remove op_kind since it encodes the information about whether the second op is register/immediate, but we already have this information in the op2 field