soc/intel/skylake: Add Sagv enum value definition

SaGv(system Agent Dynamic Frequency) have 4 settings
Disabled, Fixedlow, Fixedhigh, Enabled.
This patch add all 4 settings in enum definition and
used in devicetree.

BUG=None

Signed-off-by: Praveen hodagatta pranesh <praveenx.hodagatta.pranesh@intel.com>
Change-Id: I8f3b56f4d2bea1836373cc505ef5147144100b95
Reviewed-on: https://review.coreboot.org/c/30305
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/soc/intel/skylake/chip.h

@@ -152,7 +152,12 @@ struct soc_intel_skylake_config {
 	 * 2 = FixedHigh
 	 * 3 = Enabled
 	*/
-	u8 SaGv;
+	enum {
+		SaGv_Disabled,
+		SaGv_FixedLow,
+		SaGv_FixedHigh,
+		SaGv_Enabled,
+	} SaGv;
 
 	/* Enable/disable Rank Margin Tool */
 	u8 Rmt;