AM53C974A's Start Transfer Counter register has 24 bits, thus
maximum transfer length is 16MiB. But the maximum I can test
is 8MiB, so use that until somebody tests 16MiB.
Signed-off-by: NGuennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: NJames Bottomley <James.Bottomley@SteelEye.com>