mb/google/brya: Disable C1-state auto demotion for Brya & Brask

C1-state auto demotion feature allows hardware to determine C1-state as
per platform policy. Since Brya sets performance policy to balanced from
hardware, auto demotion can be disabled without performance impact.

Also, disabling this feature results in 110 mW power savings during
video playback.

Note that C1state Autodemotion feature is not applicable for ADL-P SoC.
Hence recommendation is to keep it disabled.

BUG=b:221876248
BRANCH=firmware-brya-14505.B
TEST=Code compiles and correct value of c1-state auto demotion is passed
to FSP. Also power and performance impact has been measure by respective
teams.

Change-Id: I41eea916cdfe4a86e4d263e3191f5cb40fa33a90
Signed-off-by: Maulik V Vaghela <maulik.v.vaghela@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/62630
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nick Vaccaro <nvaccaro@google.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>
Reviewed-by: Sridhar Siricilla <sridhar.siricilla@intel.com>

src/mainboard/google/brya/variants/baseboard/brask/devicetree.cb

@@ -76,6 +76,9 @@ chip soc/intel/alderlake
 	# FIVR RFI Spread Spectrum 1.5%
 	register "fivr_spread_spectrum" = "FIVR_SS_1_5"
 
+	# Disable C state auto-demotion for all brask baseboards
+	register "disable_c1_state_auto_demotion" = "1"
+
 	# Intel Common SoC Config
 	#+-------------------+---------------------------+
 	#| Field             |  Value                    |

src/mainboard/google/brya/variants/baseboard/brya/devicetree.cb

@@ -72,6 +72,9 @@ chip soc/intel/alderlake
 	# FIVR RFI Spread Spectrum 1.5%
 	register "fivr_spread_spectrum" = "FIVR_SS_1_5"
 
+	# Disable C state auto-demotion for all brya baseboards
+	register "disable_c1_state_auto_demotion" = "1"
+
 	# Intel Common SoC Config
 	#+-------------------+---------------------------+
 	#| Field             |  Value                    |