target-s390: Convert MVC

The code that was in gen_op_mvc was a bit confused wrt what lengths
it wanted to handle.  I also disbelieve that the inline memset is
worthwhile.

Signed-off-by: Richard Henderson <rth@twiddle.net>
diff --git a/target-s390x/insn-data.def b/target-s390x/insn-data.def
index 4d7f862..a8056a8 100644
--- a/target-s390x/insn-data.def
+++ b/target-s390x/insn-data.def
@@ -286,6 +286,7 @@
     C(0xeb9a, LAMY,    RSY_a, LD,  0, a2, 0, 0, lam, 0)
 
 /* MOVE */
+    C(0xd200, MVC,     SS_a,  Z,   la1, a2, 0, 0, mvc, 0)
     C(0xe544, MVHHI,   SIL,   GIE, la1, i2, 0, m1_16, mov2, 0)
     C(0xe54c, MVHI,    SIL,   GIE, la1, i2, 0, m1_32, mov2, 0)
     C(0xe548, MVGHI,   SIL,   GIE, la1, i2, 0, m1_64, mov2, 0)