ACPI / PCI: Make pci_slot built-in only, not a module

As discussed in thread at https://patchwork.kernel.org/patch/1946851/,
there's no value in supporting CONFIG_ACPI_PCI_SLOT=m any more.
So change Kconfig and code to only support building pci_slot as
built-in driver.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 38c5078..27fde5e8 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -308,7 +308,7 @@
 	  is about half of the penalty and is rarely useful.
 
 config ACPI_PCI_SLOT
-	tristate "PCI slot detection driver"
+	bool "PCI slot detection driver"
 	depends on SYSFS
 	default n
 	help
@@ -317,9 +317,6 @@
 	  i.e., segment/bus/device/function tuples, with physical slots in
 	  the system.  If you are unsure, say N.
 
-	  To compile this driver as a module, choose M here:
-	  the module will be called pci_slot.
-
 config X86_PM_TIMER
 	bool "Power Management Timer Support" if EXPERT
 	depends on X86