tcg-s390: Define TCG_TARGET_INSN_UNIT_SIZE

And use tcg pointer differencing functions as appropriate.

Signed-off-by: Richard Henderson <rth@twiddle.net>
diff --git a/tcg/s390/tcg-target.h b/tcg/s390/tcg-target.h
index 755c002..5bf733e 100644
--- a/tcg/s390/tcg-target.h
+++ b/tcg/s390/tcg-target.h
@@ -24,6 +24,8 @@
 #ifndef TCG_TARGET_S390 
 #define TCG_TARGET_S390 1
 
+#define TCG_TARGET_INSN_UNIT_SIZE 2
+
 typedef enum TCGReg {
     TCG_REG_R0 = 0,
     TCG_REG_R1,