arch/avr32: fix build failure caused by wrong prototype

This patch fixes a build failure introduced by 1d839317 ("avr32: use
generic ptrace_resume code") which had the static keyword as a leftover.

  arch/avr32/kernel/ptrace.c:32: error: static declaration of `user_enable_single_step' follows non-static declaration
  include/linux/ptrace.h:268: error: previous declaration of `user_enable_single_step' was here

References:
[1]http://kisskb.ellerman.id.au/kisskb/buildresult/2448162/Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/avr32/kernel/ptrace.c

@@ -28,7 +28,7 @@ static struct pt_regs *get_user_regs(struct task_struct *tsk)
 				  THREAD_SIZE - sizeof(struct pt_regs));
 }
 
-static void user_enable_single_step(struct task_struct *tsk)
+void user_enable_single_step(struct task_struct *tsk)
 {
 	pr_debug("user_enable_single_step: pid=%u, PC=0x%08lx, SR=0x%08lx\n",
 		 tsk->pid, task_pt_regs(tsk)->pc, task_pt_regs(tsk)->sr);