pds_core: Allocate pdsc_viftype_defaults copy with ARRAY_SIZE()

In preparation for making the kmalloc family of allocators type aware,
we need to make sure that the returned type from the allocation matches
the type of the variable being assigned. (Before, the allocator would
always return "void *", which can be implicitly cast to any pointer type.)

This is allocating a copy of pdsc_viftype_defaults, which is an array of
struct pdsc_viftype. To correctly return "struct pdsc_viftype *" in the
future, adjust the allocation to allocating ARRAY_SIZE-many entries. The
resulting allocation size is the same.

Signed-off-by: Kees Cook <kees@kernel.org>
Reviewed-by: Shannon Nelson <shannon.nelson@amd.com>
Link: https://patch.msgid.link/20250426060712.work.575-kees@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>