pcm: Add the PCM state checks to plugins

I noticed that some plugin codes have no proper PCM state checks and
it results in expected outcomes.  For example, when snd_pcm_drain() is
called for a dmix PCM after calling snd_pcm_drop(), it stalls
unexpectedly.  It's just because its drain callback doesn't expect the
SND_PCM_SETUP state.

We can fix such a bug in each place one by one, but a safer way would
be to filter out all such cases commonly in the PCM API functions
themselves.  This patch adds the PCM state sanity checks to major API
functions so that they return -EBADFD when called in the unexpected
PCM states.

As well as for the thread-safety extension, it'd be a question of the
performance; again at this time, the hw PCM is considered as an
exception, and it has pcm->own_state_check flag set, which means that
the common PCM state checks are skipped.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

src/pcm/pcm_local.h

@@ -234,6 +234,7 @@ struct _snd_pcm {
 					 * use the mmaped buffer of the slave
 					 */
 	unsigned int donot_close: 1;	/* don't close this PCM */
+	unsigned int own_state_check:1; /* plugin has own PCM state check */
 	snd_pcm_channel_info_t *mmap_channels;
 	snd_pcm_channel_area_t *running_areas;
 	snd_pcm_channel_area_t *stopped_areas;