ftrace/x86: Remove mcount() declaration

Commit 562e14f ("ftrace/x86: Remove mcount support") removed the
support for using mcount, so we could remove the mcount() declaration
to clean up.

Link: http://lkml.kernel.org/r/[email protected]

Signed-off-by: Jisheng Zhang <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>

Author: rvosk

arch/x86/include/asm/ftrace.h

@@ -16,7 +16,6 @@
 #define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
 
 #ifndef __ASSEMBLY__
-extern void mcount(void);
 extern atomic_t modifying_ftrace_code;
 extern void __fentry__(void);