ASoC: TrimSlice machine: Set the new fully_routed flag

Set card.fully_routed to request the ASoC core calculated unused codec
pins, and call snd_soc_dapm_nc_pin() for them. Remove the open-coded
calls.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>