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

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.

Bug: 28980217
Change-Id: Iff69ca708e0022ce9301efae798798b9bfcf9e25
Signed-off-by: Kangjie Lu <kjlu@gatech.edu>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Siqi Lin <siqilin@google.com>
(cherry picked from commit 9a47e9cff994f37f7f0dbd9ae23740d0f64f9fe6)