PCI: Convert ioapic to be builtin only, not modular

Convert pci/ioapic.c to be builtin only, with no module option, so we can
support IO-APIC hotplug.  Also make it depend on X86_IO_APIC.

[bhelgaas: changelog]
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index b6a99f7..893503f 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -105,9 +105,10 @@
 	  If unsure, say N.
 
 config PCI_IOAPIC
-	tristate "PCI IO-APIC hotplug support" if X86
+	bool "PCI IO-APIC hotplug support" if X86
 	depends on PCI
 	depends on ACPI
+	depends on X86_IO_APIC
 	default !X86
 
 config PCI_LABEL