ASoC: compress: Pass error out of soc_compr_pointer

Both soc_compr_pointer and the platform driver pointer callback return
ints but current soc_compr_pointer always returns 0. Update this so we
return the actual value from the platform driver callback. This doesn't
fix any issues simply makes the code more consistent.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>