mm: remove unused argument from create_cache()

That root_cache argument is unused so remove it.

Link: https://lore.kernel.org/r/20240828-work-kmem_cache-rcu-v3-1-5460bc1f09f6@kernel.org


Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>