regulator: docs: add missing helper

Add missing devm_regulator_bulk_get_const() to devres.rst, it's introduced
by commit 1de452a0 ("regulator: core: Allow drivers to define their init
data as const").

Fixes: 1de452a0 ("regulator: core: Allow drivers to define their init data as const")
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20221102020716.1397449-1-yangyingliang@huawei.com


Signed-off-by: Mark Brown <broonie@kernel.org>