tools/testing/crypto: Use vzalloc instead of vmalloc+memset

This fixes the corresponding coccinelle warning.

Signed-off-by: Siddh Raman Pant <code@siddh.me>
Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Link: https://lore.kernel.org/r/20220627075148.140705-1-code@siddh.me


[agordeev@linux.ibm.com added Link]
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>