platform/x86: thinkpad_acpi: Provide hotkey_poll_stop_sync() dummy

Provide a hotkey_poll_stop_sync() dummy implementation when
CONFIG_THINKPAD_ACPI_HOTKEY_POLL, so that the #ifdef-ery around
hotkey_poll_stop_sync() can be removed from hotkey_exit().
Tested-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20240424122834.19801-3-hdegoede@redhat.com

drivers/platform/x86/thinkpad_acpi.c

@@ -2575,6 +2575,9 @@ static void hotkey_poll_setup_safe(const bool __unused)
 {
 }
 
+static void hotkey_poll_stop_sync(void)
+{
+}
 #endif /* CONFIG_THINKPAD_ACPI_HOTKEY_POLL */
 
 static int hotkey_inputdev_open(struct input_dev *dev)
@@ -3045,9 +3048,7 @@ static void tpacpi_send_radiosw_update(void)
 static void hotkey_exit(void)
 {
 	mutex_lock(&hotkey_mutex);
-#ifdef CONFIG_THINKPAD_ACPI_HOTKEY_POLL
 	hotkey_poll_stop_sync();
-#endif
 	dbg_printk(TPACPI_DBG_EXIT | TPACPI_DBG_HKEY,
 		   "restoring original HKEY status and mask\n");
 	/* yes, there is a bitwise or below, we want the