mb/google/guybrush/var/dewatt: disable unused PCIe clock setting

GPP_CLK1 is used for SD and GPP_CLK2 is for WWAN on guybrush.
Disable unused PCIe GPP_CLK1 and GPP_CLK2 for dewatt.

BUG=b:211566312
TEST=emerge-guybrush coreboot

Signed-off-by: Kenneth Chan <kenneth.chan@quanta.corp-partner.google.com>
Change-Id: If449453bc60ed41e104346429babc06a73acef64
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60328
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Rob Barnes <robbarnes@google.com>

src/mainboard/google/guybrush/variants/dewatt/overridetree.cb

@@ -58,6 +58,10 @@ chip soc/amd/cezanne
 		},
 	}"
 
+        # general purpose PCIe clock output configuration
+        register "gpp_clk_config[1]" = "GPP_CLK_OFF"
+        register "gpp_clk_config[2]" = "GPP_CLK_OFF"
+
 	# I2C Config
 	#+-------------------+---------------------------+
 	#| Field             |  Value                    |