Stopping of one stream is killing the other stream when they
are running simultaneously. This is because, IER register is
cleared which disables I2S and overrides any other block enables.

Clearing IER register only when all streams on a channel are disabled,
fixes the issue.
Signed-off-by: Akshu Agrawal <akshu.agrawal@amd.com>
Link: https://lore.kernel.org/r/20200128103029.128841-1-akshu.agrawal@amd.comSigned-off-by: Mark Brown <broonie@kernel.org>