media: media/v4l2-core: Fix kernel-infoleak in video_put_user()

video_put_user() is copying uninitialized stack memory to userspace due
to the compiler not initializing holes in the structures declared on the
stack. Fix it by initializing `ev32` and `vb32` using memset().

Reported-and-tested-by:  <syzbot+79d751604cb6f29fbf59@syzkaller.appspotmail.com>
Link: https://syzkaller.appspot.com/bug?extid=79d751604cb6f29fbf59



Cc: stable@vger.kernel.org
Fixes: 1a6c0b36 ("media: v4l2-core: fix VIDIOC_DQEVENT for time64 ABI")
Fixes: 577c89b0 ("media: v4l2-core: fix v4l2_buffer handling for time64 ABI")
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>