ftrace: have function graph use mcount caller address

Impact: consistency change for function graph

This patch makes function graph record the mcount caller address
the same way the function tracer does.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 2aa0526..9060ba6 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -173,6 +173,7 @@
 
 	leaq 8(%rbp), %rdi
 	movq 0x38(%rsp), %rsi
+	subq $MCOUNT_INSN_SIZE, %rsi
 
 	call	prepare_ftrace_return