sh4: Fix inc8 and dec8 operations

We should increment and decrement by 8 according to the SH-4 Software Manual.

Signed-off-by: Magnus Damm <address@hidden>

--- 0001/target-sh4/op.c
+++ work/target-sh4/op.c	2007-04-25 16:18:47.000000000 +0900
@@ -737,7 +737,7 @@ void OPPROTO op_dec4_rN(void)
 
 void OPPROTO op_dec8_rN(void)
 {
-    env->gregs[PARAM1] -= 4;
+    env->gregs[PARAM1] -= 8;
     RETURN();
 }
 
@@ -761,7 +761,7 @@ void OPPROTO op_inc4_rN(void)
 
 void OPPROTO op_inc8_rN(void)
 {
-    env->gregs[PARAM1] += 4;
+    env->gregs[PARAM1] += 8;
     RETURN();
 }