Architectures don't need to define ISA_DMA_THRESHOLD anymore.
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: NJames Bottomley <James.Bottomley@suse.de>
Acked-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>