soc/intel/alderlake: Add IRQ mapping for PEG PCI-E ports

ACPI _PRT method was missing from PEG (SoC PCI-E) links, resulting in
OS complaining about interrupt routing:
    pcieport 0000:00:06.0: can't derive routing for PCI INT A

Tested on `starbook_adl` with Ubuntu 24.04 by running SSD
benchmark with GNOME disks and suspend.

Change-Id: I2e36cee37716d3b003b9ce250f28fdf5581a15bc
Signed-off-by: Sean Rhodes <sean@starlabs.systems>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/84620
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kapil Porwal <kapilporwal@google.com>
Reviewed-by: Jérémy Compostella <jeremy.compostella@intel.com>

src/soc/intel/alderlake/acpi/pcie.asl

@@ -309,16 +309,52 @@ Device (RP12)
 Device (PEG0)
 {
 	Name (_ADR, 0x00060000)
+
+	OperationRegion (RPCS, PCI_Config, 0x4c, 4)
+	Field (RPCS, AnyAcc, NoLock, Preserve)
+	{
+		, 24,
+		RPPN, 8,	/* Root Port Number */
+	}
+
+	Method (_PRT)
+	{
+		Return (IRQM (RPPN))
+	}
 }
 
 Device (PEG1)
 {
 	Name (_ADR, 0x00060002)
+
+	OperationRegion (RPCS, PCI_Config, 0x4c, 4)
+	Field (RPCS, AnyAcc, NoLock, Preserve)
+	{
+		, 24,
+		RPPN, 8,	/* Root Port Number */
+	}
+
+	Method (_PRT)
+	{
+		Return (IRQM (RPPN))
+	}
 }
 
 Device (PEG2)
 {
 	Name (_ADR, 0x00010000)
+
+	OperationRegion (RPCS, PCI_Config, 0x4c, 4)
+	Field (RPCS, AnyAcc, NoLock, Preserve)
+	{
+		, 24,
+		RPPN, 8,	/* Root Port Number */
+	}
+
+	Method (_PRT)
+	{
+		Return (IRQM (RPPN))
+	}
 }
 #endif
 

src/soc/intel/alderlake/acpi/pcie_pch_s.asl

@@ -275,14 +275,26 @@ Device (RP28)
 Device (PEG0)
 {
 	Name (_ADR, 0x00060000)
+	Method (_PRT)
+	{
+		Return (IRQM (1))
+	}
 }
 
 Device (PEG1)
 {
 	Name (_ADR, 0x00010000)
+	Method (_PRT)
+	{
+		Return (IRQM (1))
+	}
 }
 
 Device (PEG2)
 {
 	Name (_ADR, 0x00010001)
+	Method (_PRT)
+	{
+		Return (IRQM (2))
+	}
 }