s390x/tcg: move fallthrough annotation

...so that the compiler properly recognizes it.

Reported-by: Stefan Weil <sw@weilnetz.de>
Fixes: f180da83c0 ("s390x/tcg: Implement VECTOR LOAD LOGICAL ELEMENT AND ZERO")
Message-Id: <20190708125433.16927-3-cohuck@redhat.com>
Reviewed-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

target/s390x/translate_vx.inc.c

@@ -577,8 +577,8 @@ static DisasJumpType op_vllez(DisasContext *s, DisasOps *o)
             enr = 0;
             break;
         }
-    default:
         /* fallthrough */
+    default:
         gen_program_exception(s, PGM_SPECIFICATION);
         return DISAS_NORETURN;
     }