PCM prepare callbacks can be called multiple times. During S3
the stream registers will be reset when Controller is reset.
When stream is resumed, these stream registers needs to reconfigured.

This patch removes the check in prepare callback() if stream already
prepared, which will allow reconfiguring of stream registers and also
decouple stream when stream is resumed to route audio via DSP.
Signed-off-by: Jeeja KP <jeeja.kp@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>