ALSA: pcm: Add snd_pcm_stop_xrun() helper

Add a new helper function snd_pcm_stop_xrun() to the standard sequnce
lock/snd_pcm_stop(XRUN)/unlock by a single call, and replace the
existing open codes with this helper.

The function checks the PCM running state to prevent setting the wrong
state, too, for more safety.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
ALSA: usb-audio: Allow multiple entries for the same iface in composite quirk

Currently the composite quirk doesn't work when multiple entries are
assigned to the same interface because it marks the interface as
claimed then checks whether the interface has been already claimed for
the secondary entry.  But, if you look at the code, you'll notice that
multiple entries are allowed if the entry is the current interface;
i.e. the current behavior is anyway inconsistent, and this is an
unintended shortcoming.

This patch fixes the problem by marking the relevant interfaces as
claimed after applying the all composite entries.  This fix will be
needed for the upcoming enhancements for Digidesign Mbox 1 quirks.

Reviewed-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>