mb/google/rex/var/karis: Update fw_config FAN field

After confirm with thermal, only EC will reference FAN field in
fw_config.
Update the settings for align fw_config.

BUG=b:307822225
TEST=emerge coreboot pass

Change-Id: Id7c4cdba29c5500c06d0f2293495650bb14b9e9c
Signed-off-by: Tyler Wang <tyler.wang@quanta.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79573
Reviewed-by: Subrata Banik <subratabanik@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jakub Czapiga <czapiga@google.com>
Reviewed-by: YH Lin <yueherngl@google.com>
Reviewed-by: Eran Mitrani <mitrani@google.com>

src/mainboard/google/rex/variants/karis/overridetree.cb

@@ -11,7 +11,8 @@ fw_config
 		option ALC5650_NO_AMP_I2S	0
 	end
 	field FAN 6 7
-		option FAN_SETTING_1		0
+		option ABSENT			0
+		option PRESENT			1
 	end
 	field MIPI_CAM 8 9
 		option UF_CAM_HI556		0
@@ -250,9 +251,7 @@ chip soc/intel/meteorlake
 				register "options.fan.fine_grained_control" = "1"
 				register "options.fan.step_size" = "2"
 
-				device generic 0 alias dptf_policy on
-					probe FAN FAN_SETTING_1
-				end
+				device generic 0 alias dptf_policy on end
 			end
 		end
 		device ref pcie_rp10 on