This is all that should be listed. You’ve probably read about the A53 cores, but this is part of the low power mode.
The ARM CPUs tend to advertise the term “big.LITTLE”…which is a way to have both low power and high power without running out of battery. In essense, the A57 cores each have a “shadow” core…the shadow cores are extremely low power and great for detecting activity and then switching back to the A57 cores. The hardware in some computer architectures would require the operating system to glue these CPU cores together…big.LITTLE does this in hardware. Those “LITTLE” cores directly connect to some of the internals of the “big” cores, and do not have issues with software requirements to go back and forth between cores without programming support. Thus, they are invisible, and participate as something of a back end for the fast cores, while the fast cores are the front end. You can’t stop processing to save power…if you did, then you can’t wake up and do things like monitor for an incoming telephone call…A53 can do this with virtually no battery consumption.
There is also an ARM Cortex A9 in TX1, it is a dedicated audio processing core, and will not show up as a CPU.