mb/google/brya/var/redrix: Set RFI Spread Spectrum to 6%

Set RFI Spread Spectrum to 6% for Redrix as RF team request.
The default of Spread Spectrum in FSP is 1.5%, and set 1.5% in baseboard
as default.

BUG=b:200886627
TEST=build

Signed-off-by: Wisley Chen <wisley.chen@quanta.corp-partner.google.com>
Change-Id: Id0b42446e9e46ef629b5ca8d5d29faf2d771348d
Reviewed-on: https://review.coreboot.org/c/coreboot/+/58880
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

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

@@ -68,6 +68,9 @@ chip soc/intel/alderlake
 	register "PchHdaIDispLinkFrequency" = "HDA_LINKFREQ_96MHZ"
 	register "PchHdaIDispCodecEnable" = "1"
 
+        # FIVR RFI Spread Spectrum 1.5%
+        register "FivrSpreadSpectrum" = "FIVR_SS_1_5"
+
 	# Intel Common SoC Config
 	#+-------------------+---------------------------+
 	#| Field             |  Value                    |

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

@@ -74,6 +74,9 @@ chip soc/intel/alderlake
 	register "PchHdaIDispLinkFrequency" = "HDA_LINKFREQ_96MHZ"
 	register "PchHdaIDispCodecEnable" = "1"
 
+	# FIVR RFI Spread Spectrum 1.5%
+	register "FivrSpreadSpectrum" = "FIVR_SS_1_5"
+
 	# Intel Common SoC Config
 	#+-------------------+---------------------------+
 	#| Field             |  Value                    |

src/mainboard/google/brya/variants/redrix/overridetree.cb

@@ -34,6 +34,8 @@ chip soc/intel/alderlake
 	register "SaGv" = "SaGv_Enabled"
 
 	register "CnviBtAudioOffload" = "true"
+	# FIVR RFI Spread Spectrum 6%
+	register "FivrSpreadSpectrum" = "FIVR_SS_6"
 
 	# Intel Common SoC Config
 	#+-------------------+---------------------------+