PCI / hotplug / ACPI: Drop unused acpiphp_debug declaration

Commit bd950799 (PCI: acpiphp: Convert to dynamic debug) removed users
of acpiphp_debug variable and the variable itself but the declaration was
left in the header file. Drop this unused declaration.
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/pci/hotplug/acpiphp.h

@@ -186,7 +186,6 @@ u8 acpiphp_get_latch_status(struct acpiphp_slot *slot);
 u8 acpiphp_get_adapter_status(struct acpiphp_slot *slot);
 
 /* variables */
-extern bool acpiphp_debug;
 extern bool acpiphp_disabled;
 
 #endif /* _ACPIPHP_H */