ASoC: atmel_ssc_dai: implement left-justified data mode

Enable support for left-justified data mode for SSC-codec link.

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Reviewed-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
Link: https://lore.kernel.org/r/44fa6b700421e80778f20ff9ead2b148cf6d2e92.1566677788.git.mirq-linux@rere.qmqm.pl


Signed-off-by: Mark Brown <broonie@kernel.org>