The cpu address of a source cpu (responsible for an external irq) is only to
be stored if bit 6 of the ext irq code is set.

If bit 6 is not set, it is to be zeroed out.

The special external irq code used for virtio and pfault uses the cpu addr as a
parameter field. As bit 6 is set, this implementation is correct.
Reviewed-by: NThomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: NDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>