[S390] cleanup ftrace backend functions

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/ftrace.h b/arch/s390/include/asm/ftrace.h
index 96c14a9..3c29be4 100644
--- a/arch/s390/include/asm/ftrace.h
+++ b/arch/s390/include/asm/ftrace.h
@@ -4,20 +4,17 @@
 #ifndef __ASSEMBLY__
 
 extern void _mcount(void);
-extern unsigned long ftrace_dyn_func;
 
 struct dyn_arch_ftrace { };
 
 #define MCOUNT_ADDR ((long)_mcount)
 
 #ifdef CONFIG_64BIT
-#define MCOUNT_OFFSET_RET 18
-#define MCOUNT_INSN_SIZE  24
-#define MCOUNT_OFFSET	  14
-#else
-#define MCOUNT_OFFSET_RET 26
-#define MCOUNT_INSN_SIZE  30
+#define MCOUNT_INSN_SIZE  12
 #define MCOUNT_OFFSET	   8
+#else
+#define MCOUNT_INSN_SIZE  20
+#define MCOUNT_OFFSET	   4
 #endif
 
 static inline unsigned long ftrace_call_adjust(unsigned long addr)