s390x/kvm: Add function for injecting pgm access exceptions

s390x/kvm: Add function for injecting pgm access exceptions

Program access exceptions are defined to deliver a translation exception
code in the low-core. Add a function trigger_access_exception() that
generates the proper program interrupt on both KVM and non-KVM systems
and switch the existing code to use it.

Signed-off-by: Thomas Huth <[email protected]>
Signed-off-by: Jens Freimann <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Reviewed-by: Cornelia Huck <[email protected]>
Signed-off-by: Christian Borntraeger <[email protected]>