ALSA: pcm: Zero-clear reserved fields of PCM status ioctl in compat mode

ALSA: pcm: Zero-clear reserved fields of PCM status ioctl in compat mode

commit 317168d0c766defd14b3d0e9c2c4a9a258b803ee upstream.

In compat mode, we copy each field of snd_pcm_status struct but don't
touch the reserved fields, and this leaves uninitialized values
there.  Meanwhile the native ioctl does zero-clear the whole
structure, so we should follow the same rule in compat mode, too.

Reported-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>