clk: generalize devm_clk_get() a bit

[ Upstream commit abae8e57

 ]

Allow to add an exit hook to devm managed clocks. Also use
clk_get_optional() in devm_clk_get_optional instead of open coding it.
The generalisation will be used in the next commit to add some more
devm_clk helpers.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alexandru Ardelean <aardelean@deviqon.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20220520075737.758761-3-u.kleine-koenig@pengutronix.de
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Stable-dep-of: c61bfb1c

 ("mmc: mtk-sd: Fix missing clk_disable_unprepare in msdc_of_clock_parse()")
Signed-off-by: Sasha Levin <sashal@kernel.org>