ASoC: bcm: cygnus-pcm: Unneeded variable: "ret".

This patch fixes below issues reported by coccicheck

sound/soc/bcm/cygnus-pcm.c:642:5-8: Unneeded variable: "ret". Return "0"
on line 650
sound/soc/bcm/cygnus-pcm.c:671:5-8: Unneeded variable: "ret". Return "0"
on line 696

We cannot change return type of these functions as they are callback
functions of snd_pcm_ops

Signed-off-by: Hariprasad Kelam <hariprasad.kelam@gmail.com>
Link: https://lore.kernel.org/r/20190709184236.GA7873@hari-Inspiron-1545


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