ASoC: renesas: fsi: Use devm_clk_get_optional() for optional clocks

ASoC: renesas: fsi: Use devm_clk_get_optional() for optional clocks

The xck, ick, and div clocks are optional. Switch from devm_clk_get()
to devm_clk_get_optional() to correctly handle cases where these clocks
are missing.

Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Suggested-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: bui duc phuc <phucduc.bui@gmail.com>
Link: https://patch.msgid.link/20260609113836.45079-8-phucduc.bui@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>