ASoC: mediatek: Remove AIF widgets for backend DAIs

DAPM core already creates widgets for DAIs. It is not necessary
to declare them by SND_SOC_DAPM_AIF_IN/SND_SOC_DAPM_AIF_OUT.
Furthermore, original codes use backend DAI's stream name to be the AIF
widget name. It causes the same widget to be created twice, and after
commit 92fa1242 ("ASoC: dapm: Add new widgets to the end of the
widget list") the first created widget (by snd_soc_dapm_new_controls)
is used, not the 2nd created one (by snd_soc_dapm_new_dai_widgets),
so audio path is broken.

Signed-off-by: Koro Chen <koro.chen@mediatek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>