ASoC: fsl_ssi: Save a dev reference for dev_err() purpose.

Most of functions only receive the ssi_private reference and don't have
a knowledge of 'dev' pointer, even for debug purpose.

Signed-off-by: Arnaud Mouiche <arnaud.mouiche@invoxia.com>
Tested-by: Caleb Crome <caleb@crome.org>
Signed-off-by: Mark Brown <broonie@kernel.org>