ath_lna_div: dead ath_lna_div_ioctl() unconditionally copyouts uninitialized kernel heap (kmalloc without M_ZERO, executed even after EINVAL) - latent uninitialized-memory disclosure if ever wired up

Summary

Zero call sites tree-wide (the DF port never wired FreeBSD's dispatch), but the body is a landmine: ATH_DIAG_DYN allocates without M_ZERO, the empty switch yields EINVAL for everything, and the trailing copyout still executes - chosen-length uninitialized kernel-heap disclosure. Realistic wiring hazard given the diag ioctls themselves lacked priv checks (DF-4320). M_ZERO + copyout-on-success fix.