device: Add support for multiple PCI segment groups

Add initial support for multiple PCI segment groups. Instead of
modifying secondary in the bus struct introduce a new segment_group
struct element and keep existing common code.

Since all platforms currently only use 1 segment this is not a
functional change. On platforms that support more than 1 segment the
segment has to be set when creating the PCI domain.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: Ied3313c41896362dd989ee2ab1b1bcdced840aa8
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79927
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Martin Roth <martin.roth@amd.corp-partner.google.com>
diff --git a/src/device/pci_rom.c b/src/device/pci_rom.c
index 2592f83..cc1e5d1 100644
--- a/src/device/pci_rom.c
+++ b/src/device/pci_rom.c
@@ -230,6 +230,10 @@
 		printk(BIOS_ERR, "%s failed\n", __func__);
 		return current;
 	}
+	if (device->bus->segment_group) {
+		printk(BIOS_ERR, "VFCT only supports GPU in first PCI segment group.\n");
+		return current;
+	}
 
 	printk(BIOS_DEBUG, "           Copying %sVBIOS image from %p\n",
 			rom == (struct rom_header *)