s390: Fix a type mixup found by BEAM.


git-svn-id: svn://svn.valgrind.org/vex/trunk@2685 8f6e269a-dfd6-0310-a8e1-e2731360e62c
diff --git a/priv/host_s390_isel.c b/priv/host_s390_isel.c
index 2f42afd..21b8867 100644
--- a/priv/host_s390_isel.c
+++ b/priv/host_s390_isel.c
@@ -2460,7 +2460,7 @@
          /* DFP arithmetic ops take rounding mode only when fpext is
             installed. But, DFP quantize operation takes rm irrespective
             of fpext facility . */
-         if (s390_host_has_fpext || dfpop == Iop_QuantizeD128) {
+         if (s390_host_has_fpext || op == Iop_QuantizeD128) {
             rounding_mode = get_dfp_rounding_mode(env, irrm);
          } else {
             set_dfp_rounding_mode_in_fpc(env, irrm);