soc/intel/cannonlake: Declare SATA Mode clear

FSP support two SATA modes as AHCI mode (0) and RAID mode (1), make it
more clear in header file.

Change-Id: I1edcadc0048df839da145260b60f9f7720d981fe
Signed-off-by: Lijian Zhao <lijian.zhao@intel.com>
Reviewed-on: https://review.coreboot.org/c/30093
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/cannonlake/chip.h

@@ -124,7 +124,10 @@ struct soc_intel_cannonlake_config {
 	uint16_t usb3_wake_enable_bitmap;
 
 	/* SATA related */
-	uint8_t SataMode;
+	enum {
+		Sata_AHCI,
+		Sata_RAID,
+	} SataMode;
 	uint8_t SataSalpSupport;
 	uint8_t SataPortsEnable[8];
 	uint8_t SataPortsDevSlp[8];