s390x/kvm: Fix diagnose handling.

s390x/kvm: Fix diagnose handling.

The instruction intercept handler for diagnose used only the displacement
when trying to calculate the function code. This is only correct for base
0, however; we need to perform a complete base/displacement address
calculation and use bits 48-63 as the function code.

Reviewed-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
(cherry picked from commit 638129ff475dd3b4c0e57e0be598efe41461e9b3)

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>