ata: Fix CS55xx dependencies

As far as I know, the CS5520 and CS5530 chipsets were only used with
32-bit x86 Geode processors, so I think their drivers are only needed
on this architecture, except for build testing purpose.

While we're here, simplify the dependencies for the CS5535 driver.

The CS5536 was used with the Geode processors, but also on MIPS
Loongson/Lemote 2 systems, so let its driver be built for these two
architectures only, except for build testing purpose.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>