target/s390x: use trigger_pgm_exception() in s390_cpu_handle_mmu_fault()

This looks cleaner. linux-user will not use the ilen field, so setting
it doesn't do any harm.
Reviewed-by: NThomas Huth <thuth@redhat.com>
Signed-off-by: NDavid Hildenbrand <david@redhat.com>
Message-Id: <20170913132417.24384-10-david@redhat.com>
Signed-off-by: NCornelia Huck <cohuck@redhat.com>

target/s390x/excp_helper.c

@@ -59,8 +59,7 @@ int s390_cpu_handle_mmu_fault(CPUState *cs, vaddr address,
 {
     S390CPU *cpu = S390_CPU(cs);
 
-    cs->exception_index = EXCP_PGM;
-    cpu->env.int_pgm_code = PGM_ADDRESSING;
+    trigger_pgm_exception(&cpu->env, PGM_ADDRESSING, ILEN_AUTO);
     /* On real machines this value is dropped into LowMem.  Since this
        is userland, simply put this someplace that cpu_loop can find it.  */
     cpu->env.__excp_addr = address;