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: 30609570

Change-Id: I3c04e39cdc47e70817d93dfe5d17ac6d228a0dc7
Tracked-On: https://jira01.devtools.intel.com/browse/AW-1818


Signed-off-by: Kangjie Lu <kjlu@gatech.edu>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Erwan Mahe <erwan.mahe@intel.com>