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

(cherry pick from commit 9a47e9cf)

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: I0ba03af4d0620bcbc7a808d083295b7c97aba56d