liquidio: Replace vmalloc_node + memset with vzalloc_node and use array_size

Use vzalloc/vzalloc_node instead of the vmalloc/vzalloc_node and memset.

Also, notice that vzalloc_node() function has no 2-factor argument form
to calculate the size for the allocation, so multiplication factors need
to be wrapped in array_size().

This issue was found with the help of Coccinelle and, audited and fixed
manually.

Addresses-KSPP-ID: https://github.com/KSPP/linux/issues/83


Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>