Documentation: reset: Remove reset_controller_add_lookup()

Commit 205b261 ("reset: remove legacy reset lookup code") removed this
api, so update the document.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

Author: Yue Haibing

Documentation/driver-api/reset.rst

@@ -218,4 +218,3 @@ devm_reset_controller_register().
                reset_controller_register
                reset_controller_unregister
                devm_reset_controller_register
-               reset_controller_add_lookup