mb/google/brya: Switch to using device pointers using alias names

This change replaces the device tree walks with device pointers by
adding alias for dptf_policy generic device in the tree.

Change-Id: I8fd5476a9cea84ab8b2678167b3e0504eecacf6c
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57739
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

src/mainboard/google/brya/variants/baseboard/brya/ramstage.c

@@ -11,18 +11,14 @@
 
 #define MILLIWATTS_TO_WATTS	1000
 
+WEAK_DEV_PTR(dptf_policy);
+
 void variant_update_power_limits(const struct cpu_power_limits *limits, size_t num_entries)
 {
 	if (!num_entries)
 		return;
 
-	const struct device_path policy_path[] = {
+	const struct device *policy_dev = DEV_PTR(dptf_policy);
-		{ .type = DEVICE_PATH_PCI, .pci.devfn = SA_DEVFN_DPTF},
-		{ .type = DEVICE_PATH_GENERIC, .generic.id = 0}
-	};
-
-	const struct device *policy_dev = find_dev_nested_path(pci_root_bus(),
-							policy_path, ARRAY_SIZE(policy_path));
 	if (!policy_dev)
 		return;
 

src/mainboard/google/brya/variants/brya0/overridetree.cb

@@ -137,7 +137,7 @@ chip soc/intel/alderlake
 				register "options.fan.fine_grained_control" = "1"
 				register "options.fan.step_size" = "2"
 
-				device generic 0 on end
+				device generic 0 alias dptf_policy on end
 			end
 		end
 		device ref ipu on

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

@@ -72,7 +72,7 @@ chip soc/intel/alderlake
 					[2] = {  16, 1000 },
 					[3] = {   8,  500 }
 				}"
-				device generic 0 on end
+				device generic 0 alias dptf_policy on end
 			end
 		end
 		device ref cnvi_wifi on

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

@@ -100,7 +100,7 @@ chip soc/intel/alderlake
 				register "options.fan.fine_grained_control" = "1"
 				register "options.fan.step_size" = "2"
 
-				device generic 0 on end
+				device generic 0 alias dptf_policy on end
 			end
 		end
 		device ref ipu on

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

@@ -107,7 +107,7 @@ chip soc/intel/alderlake
 					[2] = {  16, 1000 },
 					[3] = {   8,  500 }
 				}"
-				device generic 0 on end
+				device generic 0 alias dptf_policy on end
 			end
 		end
 		device ref cnvi_wifi on

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

@@ -113,7 +113,7 @@ chip soc/intel/alderlake
 					[2] = {  16, 1000 },
 					[3] = {   8,  500 }
 				}"
-				device generic 0 on end
+				device generic 0 alias dptf_policy on end
 			end
 		end
 		device ref ipu on