ata: pata_at91 only works on sam9

The smc driver used by pata_at91 is at91sam9 specific, so building
this driver on another at91 platform results in this error:

ERROR: "sam9_smc_configure" [drivers/ata/pata_at91.ko] undefined!
ERROR: "sam9_smc_write_mode" [drivers/ata/pata_at91.ko] undefined!
ERROR: "sam9_smc_read_mode" [drivers/ata/pata_at91.ko] undefined!

This patch changes the Kconfig dependency to ensure it always works.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: linux-ide@vger.kernel.org
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>