mn10300: use Kbuild logic to include <asm-generic/sections.h>

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>