xen/arm: smmuv3: Avoid open coded arithmetic in memory allocation

xen/arm: smmuv3: Avoid open coded arithmetic in memory allocation

Backport Linux commit 98b64741d611. This is the clean backport without
any changes

kmalloc_array()/kcalloc() should be used to avoid potential overflow
when a multiplication is needed to compute the size of the requested
memory.

So turn a devm_kzalloc()+explicit size computation into an
equivalent devm_kcalloc().

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/3f7b9b202c6b6f5edc234ab7af5f208fbf8bc944.1644274051.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Will Deacon <will@kernel.org>
Origin: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 98b64741d611
Signed-off-by: Rahul Singh <rahul.singh@arm.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>