ASoC: fsl: lpc3xxx: Make some symbols static

ASoC: fsl: lpc3xxx: Make some symbols static

These symbols are not used outside of the files, make them static to fix
sparse warnings:

sound/soc/fsl/lpc3xxx-i2s.c:261:30: warning: symbol 'lpc3xxx_i2s_dai_ops' was not declared. Should it be static?
sound/soc/fsl/lpc3xxx-i2s.c:271:27: warning: symbol 'lpc3xxx_i2s_dai_driver' was not declared. Should it be static?
sound/soc/fsl/lpc3xxx-pcm.c:55:39: warning: symbol 'lpc3xxx_soc_platform_driver' was not declared. Should it be static?

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Link: https://patch.msgid.link/20240802101044.3302251-1-yuehaibing@huawei.com
Signed-off-by: Mark Brown <broonie@kernel.org>