pcm: dmix: resume workaround for buggy driver

pcm: dmix: resume workaround for buggy driver

The previous commit removed the whole handling of resume in dmix, but
this seems causing another regression; some buggy drivers assume that
the device-resume needs to be triggered before transitioning to
PREPARED state.  As an ugly workaround, in this patch, when the slave
PCM supports resume, snd_pcm_direct_resume() does resume of the slave
PCM but immediately drop the stream after that.  In that way, the
device is brought to the sane active state, then the apps can prepare
and restart the stream properly.

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