ASoC: dapm_widget_show_codec: Use component instead of CODEC

There is nothing snd_soc_codec specific in this function, just use
snd_soc_component instead.

With this also the last reference of snd_soc_codec form soc-dapm.c.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@kernel.org>