pcm186x_dai_ops and pcm186x_adc_input_channel_sel_value are local to the
source and do not need to be in global scope, so make them static.

Cleans up sparse warnings:
symbol 'pcm186x_dai_ops' was not declared. Should it be static?
symbol 'pcm186x_adc_input_channel_sel_value' was not declared. Should it
be static?
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NMark Brown <broonie@kernel.org>