ASoC: at91sam9g20ek: Automatically disconnect non-connected pins

According to the schematics the both LHPOUT and RHPOUT are connected to the
external connector. RHPOUT is missing from the DAPM routes, but otherwise
they seem to be complete.

This patch adds the missing route and then sets the fully_routed flag for
the card. This allows to remove all the manual calls to
snd_soc_dapm_nc_pin().

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>