Use kzalloc instead of kmalloc + memset.

The semantic patch that makes this change is:
(https://coccinelle.gitlabpages.inria.fr/website/)

//<smpl>
@@
expression res, size, flag;
@@
- res = kmalloc(size, flag);
+ res = kzalloc(size, flag);
  ...
- memset(res, 0, size);
//</smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://lore.kernel.org/r/20220312102705.71413-3-Julia.Lawall@inria.frSigned-off-by: Jakub Kicinski <kuba@kernel.org>