arc: do not export symbols in troubleshoot.c

print_task_path_n_nm() is local to this file, its only user being
show_regs().  Mark the function static and avoid the EXPORT_SYMBOL.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Vineet Gupta <vgupta@synoipsys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>