ASoC: Cleanup duplicated const

Commit 85e7652d

("ASoC: Constify snd_soc_dai_ops structs") accidentally
introduced a few duplicated consts. This patch cleans it up.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>