ACPI: Remove unused extern declaration acpi_paddr_to_node()

This is never used since commit 1e3590e2 ("[PATCH] pgdat allocation
for new node add (get node id by acpi)").
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

include/linux/acpi.h

@@ -477,8 +477,6 @@ static inline int acpi_get_node(acpi_handle handle)
 	return 0;
 }
 #endif
-extern int acpi_paddr_to_node(u64 start_addr, u64 size);
-
 extern int pnpacpi_disabled;
 
 #define PXM_INVAL	(-1)