MAINTAINERS: add tree for kvm.git

Cc: Gleb Natapov <gleb@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Documentation/kvm: add a 00-INDEX file

Cc: Gleb Natapov <gleb@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>