PCI: label: remove #include of ACPI header to avoid warnings

I found that including acpi/apci_drivers.h is not necessary and
introduces these warnings:

In file included from drivers/pci/pci-label.c:32:
include/acpi/acpi_drivers.h:103: warning: ‘struct acpi_device’ declared inside parameter list
include/acpi/acpi_drivers.h:103: warning: its scope is only this definition or declaration, which is probably not what you want
include/acpi/acpi_drivers.h:107: warning: ‘struct acpi_pci_root’ declared inside parameter list
Signed-off-by: NShyam Iyer <shyam_iyer@dell.com>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/pci-label.c

@@ -29,7 +29,6 @@
 #include <linux/nls.h>
 #include <linux/acpi.h>
 #include <linux/pci-acpi.h>
-#include <acpi/acpi_drivers.h>
 #include <acpi/acpi_bus.h>
 #include "pci.h"