KVM: arm64: Mark kvm_arm_init() and its unique descendants as __init

Tag kvm_arm_init() and its unique helper as __init, and tag data that is
only ever modified under the kvm_arm_init() umbrella as read-only after
init.

Opportunistically name the boolean param in kvm_timer_hyp_init()'s
prototype to match its definition.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20221130230934.1014142-21-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>