ASoC: ti: omap-mcbsp: Ignore errors for getting fck_src

Commit 349355ce ("ARM: OMAP2+: Drop legacy platform data for omap4 mcbsp")
dropped prcm_fck for omap4, so the clk_src might not be available making the
clk_get(src) fail. In such cases, rely on the devicetree to assign
the correct parent.

Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
Link: https://lore.kernel.org/r/20230705190324.355282-2-andreas@kemnade.info


Signed-off-by: Mark Brown <broonie@kernel.org>