UPSTREAM: ALSA: timer: Fix leak in events via snd_timer_user_tinterrupt

(cherry pick from commit e4ec8cc8)

The stack object “r1” has a total size of 32 bytes. Its field
“event” and “val” both contain 4 bytes padding. These 8 bytes
padding bytes are sent to user without being initialized.

Signed-off-by: Kangjie Lu <kjlu@gatech.edu>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Bug: 28980217
Change-Id: I756d05a328a133c1c67132301434c6817be0a2a6