ata: fix i.MX AHCI driver dependencies

The ahci_imx driver is only needed on Freescale i.MX platforms so
don't let it be built on other platforms, except for build test
purpose.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Richard Zhu <r65037@freescale.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

drivers/ata/Kconfig

@@ -116,7 +116,7 @@ config AHCI_ST
 
 config AHCI_IMX
 	tristate "Freescale i.MX AHCI SATA support"
-	depends on MFD_SYSCON
+	depends on MFD_SYSCON && (ARCH_MXC || COMPILE_TEST)
 	help
 	  This option enables support for the Freescale i.MX SoC's
 	  onboard AHCI SATA.