KVM: selftests: Rename MP_STATE and GUEST_DEBUG helpers for consistency

Move the get/set part of the MP_STATE and GUEST_DEBUG helpers to the end
to align with the many other ioctl() wrappers/helpers.  Note, this is not
an endorsement of the predominant style, the goal is purely to provide
consistency in the selftests.

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