Raspberry Pi 4 ethernet support added to -current

[Jared McNeill <jmcneill%invisible.ca@localhost>]

Hi folks --

I've committed support for the Raspberry Pi 4's ethernet controller to 
NetBSD -current:

  genet0 at acpi0 (ETH0, BCM6E4E-0): mem 0xfd580000-0xfd58ffff irq 189,190
  genet0: GENETv5.0
  genet0: Ethernet address f2:00:99:06:77:87
  brgphy0 at genet0 phy 1: BCM54213PE 1000BASE-T media interface, rev. 2
  brgphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, 1000baseT, 1000baseT-FDX, auto

I have tested it both in FDT mode and in ACPI mode with the UEFI firmware 
from here: 
https://github.com/pftf/RPi4/releases/download/v1.1/RPi4_UEFI_Firmware_v1.1.zip

Note that in ACPI mode you will get a random MAC address at boot. This 
will be sorted out with a future RPi4 UEFI firmware release.

Please try it out and let me know if you run into any issues!

Cheers,
Jared