ASoC: ES8389: convert to devm_clk_get_optional() to get clock

ASoC: ES8389: convert to devm_clk_get_optional() to get clock

When enabling ES8390 via ACPI description, es8389 would fail to
obtain a clock source, causing the driver to fail to initialize.
This was not an issue with older kernels, but since commit
abae8e57e49a ("clk: generalize devm_clk_get() a bit"),
devm_clk_get() would return an error pointer when a clock source
was not detected (instead of falling back to a static clock),
causing the driver to fail early.

Use devm_clk_get_optional() instead to return to the previous
behaviour, allowing the use of a static clock source.

Cc: stable@vger.kernel.org
Signed-off-by: Li Jian <lazycat-xiao@foxmail.com>
Link: https://patch.msgid.link/tencent_7C78374FB9F4B3A37101E5C719715D8BC40A@qq.com
Signed-off-by: Mark Brown <broonie@kernel.org>