slab: add struct kmem_cache_args

slab: add struct kmem_cache_args

Currently we have multiple kmem_cache_create*() variants that take up to
seven separate parameters with one of the functions having to grow an
eigth parameter in the future to handle both usercopy and a custom
freelist pointer.

Add a struct kmem_cache_args structure and move less common parameters
into it. Core parameters such as name, object size, and flags continue
to be passed separately.

Add a new function __kmem_cache_create_args() that takes a struct
kmem_cache_args pointer and port do_kmem_cache_create_usercopy() over to
it.

In follow-up patches we will port the other kmem_cache_create*()
variants over to it as well.

Reviewed-by: Kees Cook <kees@kernel.org>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>