ASoC: Intel: byt/hsw: Add missing kthread_stop to error/cleanup path

Baytrail and Haswell SST IPC don't stop the kernel thread in error and
cleanup path thus leaving orphan kernel thread behind in such a case.

Also while at it, fix one error path in sst-haswell-ipc.c that doesn't free
hsw->msg.

[Jarkko: I edited the commit log a little]
Signed-off-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>