arch/x86/kernel/ptrace.c: Quiet sparse noise

ptrace_set_debugreg() is only used in this file and should be
static.  This also quiets the following sparse warning:

  warning: symbol 'ptrace_set_debugreg' was not declared. Should it be static?
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: hartleys@visionengravers.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/ptrace.c

@@ -749,7 +749,8 @@ static int ptrace_set_breakpoint_addr(struct task_struct *tsk, int nr,
 /*
  * Handle PTRACE_POKEUSR calls for the debug register area.
  */
-int ptrace_set_debugreg(struct task_struct *tsk, int n, unsigned long val)
+static int ptrace_set_debugreg(struct task_struct *tsk, int n,
+			       unsigned long val)
 {
 	struct thread_struct *thread = &(tsk->thread);
 	int rc = 0;