Remove the ie(4) driver for Intel 82586 ISA Ethernet adapters.

This driver only supports 10Mb Ethernet using PIO (the hardware supports
DMA, but the driver only does PIO). There are not any PCCard adapters
supported by this driver, only ISA cards. In addition, it does not use
bus_space but instead uses bcopy with volatile pointers triggering a
host of warnings. (if_ie.c is one of 3 files always built with
-Wno-error)

Relnotes: yes