skylake mainboards: Use enum values for SaGv

Replace `3` with `SaGv_Enabled`, which has the same value.

Change-Id: I05cfddfefc45ba5bfb0e684445a6d8e02d7865e3
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/52098
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Michael Niewöhner <foss@mniewoehner.de>
diff --git a/src/mainboard/purism/librem_skl/devicetree.cb b/src/mainboard/purism/librem_skl/devicetree.cb
index 47a9a5c..84efd6a 100644
--- a/src/mainboard/purism/librem_skl/devicetree.cb
+++ b/src/mainboard/purism/librem_skl/devicetree.cb
@@ -54,7 +54,7 @@
 	register "ScsEmmcHs400Enabled" = "0"
 	register "SkipExtGfxScan" = "1"
 	register "HeciEnabled" = "0"
-	register "SaGv" = "3"
+	register "SaGv" = "SaGv_Enabled"
 	register "PmConfigSlpS3MinAssert" = "2"		# 50ms
 	register "PmConfigSlpS4MinAssert" = "1"		# 1s
 	register "PmConfigSlpSusMinAssert" = "3"	# 500ms