ASoC: stm32: sai: Use the devm_clk_get_optional() helper

ASoC: stm32: sai: Use the devm_clk_get_optional() helper

[ Upstream commit 374628fb668e50b42fe81f2a63af616182415bcd ]

Use devm_clk_get_optional() instead of hand writing it.
This saves some LoC and improves the semantic.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/f7987f18dadf77bfa09969fd4c82d5a0f4e4e3b7.1684594838.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Mark Brown <broonie@kernel.org>
Stable-dep-of: 312ec2f0d9d1 ("ASoC: stm32: sai: fix clk prepare imbalance on probe failure")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>