CVE-2026-53248: net: airoha: Fix use-after-free in metadata dst teardown

In the Linux kernel, the following vulnerability has been resolved:

net: airoha: Fix use-after-free in metadata dst teardown

airohametadatadstfree() runs metadatadstfree() which frees the metadatadst with kfree() immediately, bypassing the RCU grace period. In the RX path, skbdstsetnoref() sets a non-refcounted pointer from the skb to the metadatadst. This function requires RCU read-side protection and the dst must remain valid until all RCU readers complete. Since metadatadstfree() calls kfree() directly, an use-after-free can occur if any skb still holds a noref pointer to the dst when the driver tears it down. Replace metadatadstfree() with dstrelease() which properly goes through the refcount path: when the refcount drops to zero, it schedules the actual free via callrcuhurry(), ensuring all RCU readers have completed before the memory is freed.