mainboard/google/{poppy,soraka}: Enable S0ix

Enable S0ix for poppy and soraka in their device trees respectively.

BUG=b:36630881
BRANCH=none
TEST=Verified S0ix and S3 operation on Poppy and Soraka (250+ iterations).

Change-Id: I9ba91499e54f729970448af6f71804ad5b3cb836
Signed-off-by: Rajat Jain <rajatja@google.com>
Signed-off-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://review.coreboot.org/20689
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
diff --git a/src/mainboard/google/poppy/variants/soraka/devicetree.cb b/src/mainboard/google/poppy/variants/soraka/devicetree.cb
index 9b8a18c..3de9854 100644
--- a/src/mainboard/google/poppy/variants/soraka/devicetree.cb
+++ b/src/mainboard/google/poppy/variants/soraka/devicetree.cb
@@ -24,6 +24,9 @@
 	# Enable DPTF
 	register "dptf_enable" = "1"
 
+	# Enable S0ix
+	register "s0ix_enable" = "1"
+
 	# FSP Configuration
 	register "ProbelessTrace" = "0"
 	register "EnableLan" = "0"