ASoC: rx51: Automatically disconnect non-connected pins

According to the schematics the external speaker is differential, so the
HPLCOM and HPRCOM pins of the CODEC should be connected to it.

Otherwise the routing looks complete, so add the missing routes and set the
fully_routed flag of the card instead of manually marking the unused inputs
and outputs as not connected. This makes the code a bit shorter and
cleaner.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Tested-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Reviewed-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>