soc/amd/common/block/acpi.ivrs: use SMBUS_DEVFN for FCH IOAPIC device ID

Instead of using PCI_DEVFN(SMBUS_DEV, SMBUS_FUNC), use the equivalent
SMBUS_DEVFN define.

Even though the FCH IOAPIC is in the LPC part of the FCH, it needs the
IVRS IOAPIC table's source_dev_id field set to SMBUS_DEVFN which is the
function 0 of the FCH PCI device. LPC is function 3 of the FCH device.

When assigning LPC_DEVFN to source_dev_id, the kernel from Ubuntu
2022.04 LTS complains about the IOAPIC part of the IVRS table being
wrong:

AMD-Vi: [Firmware Bug]: : No southbridge IOAPIC found
AMD-Vi: Disabling interrupt remapping

With SMBUS_DEVFN being used as source_dev_id, no such error is reported.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Suggested-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Change-Id: I8470d67b2513031e75fb422d4c1c181e017ace0a
Reviewed-on: https://review.coreboot.org/c/coreboot/+/70503
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martin.roth@amd.corp-partner.google.com>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
diff --git a/src/soc/amd/common/block/acpi/ivrs.c b/src/soc/amd/common/block/acpi/ivrs.c
index 8923463..8a03c62 100644
--- a/src/soc/amd/common/block/acpi/ivrs.c
+++ b/src/soc/amd/common/block/acpi/ivrs.c
@@ -29,7 +29,7 @@
 				   IVHD_DTE_SYS_MGT_NO_TRANS | IVHD_DTE_NMI_PASS |
 				   IVHD_DTE_EXT_INT_PASS | IVHD_DTE_INIT_PASS;
 	ivhd_ioapic->handle = get_ioapic_id(VIO_APIC_VADDR);
-	ivhd_ioapic->source_dev_id = PCI_DEVFN(SMBUS_DEV, SMBUS_FUNC);
+	ivhd_ioapic->source_dev_id = SMBUS_DEVFN; /* function 0 of FCH PCI device */
 	ivhd_ioapic->variety = IVHD_SPECIAL_DEV_IOAPIC;
 	current += sizeof(ivrs_ivhd_special_t);
 
@@ -53,7 +53,7 @@
 	ivhd_hpet->reserved = 0x0000;
 	ivhd_hpet->dte_setting = 0x00;
 	ivhd_hpet->handle = 0x00;
-	ivhd_hpet->source_dev_id = PCI_DEVFN(SMBUS_DEV, SMBUS_FUNC);
+	ivhd_hpet->source_dev_id = SMBUS_DEVFN; /* function 0 of FCH PCI device */
 	ivhd_hpet->variety = IVHD_SPECIAL_DEV_HPET;
 	current += sizeof(ivrs_ivhd_special_t);