Replace CONFIG_PCI_ROOT1/2 with CONFIG_EXTRA_PCI_ROOTS.

Instead of defining the bus id of each extra root bus, define the
number of extra root buses.  The bus id isn't necessarily stable from
one boot to the next.
diff --git a/src/Kconfig b/src/Kconfig
index bbed963..70e3509 100644
--- a/src/Kconfig
+++ b/src/Kconfig
@@ -201,19 +201,15 @@
             Support parallel ports. This also enables int 17 parallel port calls.
 
     config EXTRA_PCI_ROOTS
-        bool "Extra root buses"
-        default n
+        int "Number of extra root buses"
+        default 0
         help
-            If the target machine has multiple independent root buses,
-            the extra buses may be specified here.
-    config PCI_ROOT1
-        depends on EXTRA_PCI_ROOTS
-        hex "Extra primary PCI root bus number"
-        default 0x00
-    config PCI_ROOT2
-        depends on EXTRA_PCI_ROOTS
-        hex "Extra secondary PCI root bus number"
-        default 0x00
+            If the target machine has multiple independent root buses
+            set this to a positive value.  The SeaBIOS PCI probe will
+            then search for the given number of extra root buses.
+
+            Most machines do not have multiple root buses and this
+            setting should be zero.
 
     config USE_SMM
         depends on !COREBOOT
diff --git a/src/pci.c b/src/pci.c
index 0de8ec5..23a6878 100644
--- a/src/pci.c
+++ b/src/pci.c
@@ -93,16 +93,12 @@
 pci_probe(void)
 {
     dprintf(3, "PCI probe\n");
-    if (CONFIG_PCI_ROOT1 && CONFIG_PCI_ROOT1 > MaxPCIBus)
-        MaxPCIBus = CONFIG_PCI_ROOT1;
-    if (CONFIG_PCI_ROOT2 && CONFIG_PCI_ROOT2 > MaxPCIBus)
-        MaxPCIBus = CONFIG_PCI_ROOT2;
-
     struct pci_device *busdevs[256];
     memset(busdevs, 0, sizeof(busdevs));
     struct pci_device **pprev = &PCIDevices;
     int bus = -1, lastbus = 0, rootbuses = 0, count=0;
-    while (bus < MaxPCIBus) {
+    while (bus < 0xff && (bus < MaxPCIBus
+                          || rootbuses < CONFIG_EXTRA_PCI_ROOTS)) {
         bus++;
         int bdf;
         foreachbdf(bdf, bus) {
@@ -125,6 +121,8 @@
                     rootbuses++;
                 lastbus = bus;
                 rootbus = rootbuses;
+                if (bus > MaxPCIBus)
+                    MaxPCIBus = bus;
             } else {
                 rootbus = parent->rootbus;
             }