MFC r256806, r256919, r257167:

  Add a driver for the Freescale Fast Ethernet Controller found on various
  Freescale SoCs including the i.MX series.  This also works for the newer
  SoCs with the ENET gigabit controller, but doesn't use any of the new
  hardware features other than enabling gigabit speed.

  Mask out non-address bits in the mac address register, for proper
  detection of an all-zeroes address.  Also remove a misplaced return.

  Switch to using ofw_bus_search_compatible() table-driven compat lookup.
  Add compat strings for Freescale Vybrid family SoCs.
MFC r256809: Add configuration for the Freescale i.MX53 Quick Start Board.