binfmts.h: include list.h

linux_binfmt uses list_head, so list.h is needed.

[akpm@linux-foundation.org: fix `make headerscheck']
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>