sim: mips: drop unused ENGINE_ISSUE_POSTFIX_HOOK

Nothing defines this, and it isn't called in all the engine runtimes,
so drop it entirely to avoid confusion.
diff --git a/sim/mips/m16run.c b/sim/mips/m16run.c
index c8caeb1..ffc1031 100644
--- a/sim/mips/m16run.c
+++ b/sim/mips/m16run.c
@@ -58,10 +58,6 @@
 	  nia = m32_idecode_issue (sd, instruction_0, cia);
 	}
 
-#if defined (ENGINE_ISSUE_POSTFIX_HOOK)
-      ENGINE_ISSUE_POSTFIX_HOOK ();
-#endif
-
       /* Update the instruction address */
       cia = nia;
 
diff --git a/sim/mips/micromipsrun.c b/sim/mips/micromipsrun.c
index 86868fa..1c1475e 100644
--- a/sim/mips/micromipsrun.c
+++ b/sim/mips/micromipsrun.c
@@ -121,10 +121,6 @@
 	  nia = NULL_CIA;
 	}
 
-#if defined (ENGINE_ISSUE_POSTFIX_HOOK)
-      ENGINE_ISSUE_POSTFIX_HOOK ();
-#endif
-
       /* Update the instruction address */
       cia = nia;