kernel: remove layer of indirection for ether_input()

Mop up after the recent changes by pulling the old switcheroo
on ether_input_pkt(), effectively renaming the function to
ether_input().  Also updates comments accordingly.
kernel - Fix PF tables (SMP work)

* SMP work broke pf_table.c to some degree due to the use of globals
  to store temporary data.  The concurrency could cause table lookups
  to return an incorrect match or mismatch.

* Change pfr_sin, pfr_sin6, and pfr_mask to local variables.