Check the return value for error when processing replies and notifications.

The patch 22981243: "ASoC: Intel: Add Haswell/Broadwell IPC" from
> Feb 20, 2014, leads to the following imaginary static checker warning:
>
> 	sound/soc/intel/sst-haswell-ipc.c:898 hsw_irq_thread()
> 	warn: this is always true.
>
> sound/soc/intel/sst-haswell-ipc.c
>    895                  /* Handle Immediate reply from DSP Core */
>    896                  handled = hsw_process_reply(hsw, ipcx);
>                                   ^^^^^^^^^^^^^^^^^
> Returns 1 on success/error and -EIO on error.
>
>    897
>    898                  if (handled) {
>    899                          /* clear DONE bit - tell DSP we have completed */
>    900                          sst_dsp_shim_update_bits_unlocked(sst, SST_IPCX,
>    901                                  SST_IPCX_DONE, 0);
>    902
>    903                          /* unmask Done interrupt */
>    904                          sst_dsp_shim_update_bits_unlocked(sst, SST_IMRX,
>    905                                  SST_IMRX_DONE, 0);
>    906                  }
>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>