In the previous implementation, cxd56_stop() checked the internal
state before sending AUDIO_MSG_STOP to the message queue. However,
if the worker thread took time to turn on AMP, cxd560_stop() was
not able to send the message and caused a deadlock.
This commit fixes this issue by always sending AUDIO_MSG_STOP
regardless of the internal state.
Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>