Instead of using cpu0 and irq=0 for the IPI test, use something
a bit more interesting. To make sure we can still run the test
with the minimal number of cpus (2), we need to use sender=1. As
the irq in the test (an SGI) can only be 0 to 15 and there's really
no difference, then use irq=1. sender=1 is a bit limited for the
long term, as we may want to test IPIs across host sockets with
pinned vcpus. But we can improve on this later, possibly with the
introduction of a command line parameter.

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Andrew Jones <drjones@redhat.com>