arch/nios2/mm/fault.c: remove duplicate include

Remove linux/ptrace.h which is included more than once

Link: http://lkml.kernel.org/r/5c45d345.1c69fb81.d90ed.8e05@mx.google.com
Signed-off-by: Sabyasachi Gupta <sabyasachi.linux@gmail.com>
Cc: Ley Foon Tan <lftan@altera.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>