ALSA: pcm: Don't leave PREPARED state after draining

commit 70372a7566b5e552dbe48abdac08c275081d8558 upstream.

When a PCM draining is performed to an empty stream that has been
already in PREPARED state, the current code just ignores and leaves as
it is, although the drain is supposed to set all such streams to SETUP
state.  This patch covers that overlooked case.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>