staging: unisys: visorutil: Use kzalloc instead of kmalloc with memset

Fix coccinelle warnings of better allocation by using kzalloc.
In these cases, kzalloc is preferred, as kmalloc may fail if it does not find
contiguous memory.

Signed-off-by: Iulia Manda <iulia.manda21@gmail.com>
Acked-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>
Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>