mn10300: remove duplicated #include

Remove duplicated #include('s) in
  arch/mn10300/kernel/sys_mn10300.c

Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>