ALSA: rawmidi - fix the uninitalized user_pversion

The user_pversion was uninitialized for the user space file structure
in the open function, because the file private structure use
kmalloc for the allocation.

The kernel ALSA sequencer code clears the file structure, so no additional
fixes are required.

Cc: stable@kernel.org
Cc: broonie@kernel.org
BugLink: https://github.com/alsa-project/alsa-lib/issues/178
Fixes: 09d23174

 ("ALSA: rawmidi: introduce SNDRV_RAWMIDI_IOCTL_USER_PVERSION")
Reported-by:  <syzbot+88412ee8811832b00dbe@syzkaller.appspotmail.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20211218123925.2583847-1-perex@perex.cz
Signed-off-by: Takashi Iwai <tiwai@suse.de>