target-arm: A64: Make cache ID registers visible to AArch64

target-arm: A64: Make cache ID registers visible to AArch64

Make the cache ID system registers (CLIDR, CSSELR, CCSIDR, CTR)
visible to AArch64. These are mostly simple 64-bit extensions of the
existing 32 bit system registers and so can share reginfo definitions.
CTR needs to have a split definition, but we can clean up the
temporary user-mode implementation in favour of using the CPU-specified
reset value, and implement the system-mode-required semantics of
restricting its EL0 accessibility if SCTLR.UCT is not set.

Signed-off-by: Peter Maydell <[email protected]>
Reviewed-by: Peter Crosthwaite <[email protected]>