ASoC: sam9g20_wm8731: Convert to table based DAPM setup

Use table based setup to register the DAPM widgets and routes. This on one hand
makes the code a bit shorter and cleaner and on the other hand the board level
DAPM elements get registered in the card's DAPM context rather than in the
CODEC's DAPM context.

While we are at it also remove the snd_soc_dapm_enable_pin() in the init
callback. Pins are enabled by default.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Tested-by: Bo Shen <voice.shen@atmel.com>
Acked-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>