ata: ahci_st: Enable compile test

Enable compiling the ahci_st driver when COMPILE_TEST is enabled.
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>

drivers/ata/Kconfig

@@ -188,7 +188,7 @@ config AHCI_DWC
 
 config AHCI_ST
 	tristate "ST AHCI SATA support"
-	depends on ARCH_STI
+	depends on ARCH_STI || COMPILE_TEST
 	select SATA_HOST
 	help
 	  This option enables support for ST AHCI SATA controller.