ASoC: codecs: rt5640: Simplify mclk initialization

ASoC: codecs: rt5640: Simplify mclk initialization

Most of clk_xxx() functions do check if provided clk-pointer is
non-NULL. These do not check if the pointer is an error-pointer.
Providing such to a clk_xxx() results in a panic.

rt5640_set_dai_sysclk() is an example of that - clk_set_rate() is not
guarded by IS_ERR().

By utilizing _optional() variant of devm_clk_get() the driver code is
both simplified and more robust. There is no need to remember about
IS_ERR(clk) checks each time mclk is accessed.

Reviewed-by: Amadeusz Sławiński <amadeuszx.slawinski@linux.intel.com>
Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
Link: https://msgid.link/r/20240221152516.852353-6-cezary.rojewski@intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>