target/arm: Add Cortex-A55 CPU

target/arm: Add Cortex-A55 CPU

The Cortex-A55 is one of the newer armv8.2+ CPUs; in particular
it supports the Privileged Access Never (PAN) feature. Add
a model of this CPU, so you can use a CPU type on the virt
board that models a specific real hardware CPU, rather than
having to use the QEMU-specific "max" CPU type.

Signed-off-by: Timofey Kutergin <tkutergin@gmail.com>
Message-id: 20221121150819.2782817-1-tkutergin@gmail.com
[PMM: tweaked commit message]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>