ASoC: SOF: Don't allow pointer operations on unconfigured streams

When reporting the pointer for a compressed stream we report the current
I/O frame position by dividing the position by the number of channels
multiplied by the number of container bytes. These values default to 0 and
are only configured as part of setting the stream parameters so this allows
a divide by zero to be configured. Validate that they are non zero,
returning an error if not

Fixes: c1a731c71359 ("ASoC: SOF: compress: Add support for computing timestamps")
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org