Add the combined mode for ATI SB700

Besides those modes in ATI SB600 SATA controller, ATI SB700 supports one
more mode:the combined mode.

The combined mode is a Legacy IDE mode used for compatibility with some old
OS without AHCI driver, but now it is not necessary for Linux since the
kernel has supported AHCI.

Signed-off-by: Luugi Marsan <luugi.marsan@amd.com>
Cc: Jeff Garzik <jeff@garzik.org>
Cc: Tejun Heo <htejun@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>