[power] Fix #ifdef in ACPI sleep code.

Remove dependency on CONFIG_SOFTWARE_SUSPEND, since CONFIG_ACPI_SLEEP is 
sufficient. 

From Pavel Machek.

drivers/acpi/sleep/main.c

@@ -22,6 +22,7 @@ ACPI_MODULE_NAME		("sleep")
 u8 sleep_states[ACPI_S_STATE_COUNT];
 
 extern void do_suspend_lowlevel_s4bios(int);
+extern void do_suspend_lowlevel(int);
 
 /**
  * acpi_system_restore_state - OS-specific restoration of state
@@ -181,12 +182,11 @@ acpi_system_suspend(
 		status = acpi_enter_sleep_state(state);
 		break;
 
-#ifdef CONFIG_SOFTWARE_SUSPEND
 	case ACPI_STATE_S2:
 	case ACPI_STATE_S3:
 		do_suspend_lowlevel(0);
 		break;
-#endif
+
 	case ACPI_STATE_S4:
 		do_suspend_lowlevel_s4bios(0);
 		break;