dm-crypt: Adjust crypt_alloc_tfms_aead() allocation type

dm-crypt: Adjust crypt_alloc_tfms_aead() allocation type

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.)

The assigned type is "struct crypto_skcipher **" but the returned type
will be "struct crypto_aead **". These are the same allocation size
(pointer size), but the types don't match. Adjust the allocation type
to match the assignment.

Link: https://patch.msgid.link/20250426061629.work.266-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>