netisr: Add netisr_hashcpu, which maps pkt hash to cpuid
netisr: Renaming, cpufn -> hashfn; no functional changes
netisr: Fix comment
ip_demux: Remove unused udp_mpsafe_thread global variable
ip_demux: Save raw hash, instead of hash masked w/ ncpus2_mask, i.e. cpuid
toeplitz: Return raw hash

Currently only 16 bits are valid, since the key is seeded with 2 bytes.