kvm tools: Modify 'kvm setup' parameters

This patch makes the name as the default parameter, this makes usability
easier since this is the only parameter available at the moment anyway.

Suggested-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>