KVM: arm64: pkvm: Drop sysregs that should never be routed to the host

A bunch of system registers (most of them MM related) should never
trap to the host under any circumstance. Keep them close to our chest.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Link: https://lore.kernel.org/r/20211013120346.2926621-6-maz@kernel.org