QNZ : switch to another Queue if source register is Not Zero

The processor will change the CQ register if the source register (in SRC1) is Not Zero.

The current queue is then given by the 2-bit field located in SRC2.

The Imm16 field is used to XOR the register with a sign-extended 16-bit immediate value, so the source register can also be tested for equality with a 16-bit value.