Replace kmalloc followed by a memset with kzalloc.

Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>
Acked-by: Mike Isely <isely@pobox.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
[hverkuil-cisco@xs4all.nl: add pvrusb2: prefix in Subject]
[hverkuil-cisco@xs4all.nl: fix checkpatch whitespace warnings]
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>