[power] Fix up compiler warnings.

arch/i386/kernel/acpi/sleep.c

@@ -15,6 +15,8 @@ unsigned long acpi_wakeup_address = 0;
 unsigned long acpi_video_flags;
 extern char wakeup_start, wakeup_end;
 
+extern void zap_low_mappings(void);
+
 extern unsigned long FASTCALL(acpi_copy_wakeup_routine(unsigned long));
 
 static void init_low_mapping(pgd_t *pgd, int pgd_limit)

drivers/acpi/sleep/main.c

@@ -21,6 +21,8 @@ ACPI_MODULE_NAME		("sleep")
 
 u8 sleep_states[ACPI_S_STATE_COUNT];
 
+extern void do_suspend_lowlevel_s4bios(int);
+
 /**
  * acpi_system_restore_state - OS-specific restoration of state
  * @state:	sleep state we're exiting