KVM: arm64: Rip out the vestiges of the 'old' ID register scheme

There's no longer a need for the baggage of the old scheme for handling
configurable ID register fields. Rip it all out in favor of the
generalized infrastructure.

Link: https://lore.kernel.org/r/20230609190054.1542113-12-oliver.upton@linux.dev


Signed-off-by: Oliver Upton <oliver.upton@linux.dev>