initrd: add devicetree support

This adds capability to hand over the network configuration from
OpenFirmware (and potentially other boot loaders with openfirmware
support such as U-Boot) to NetworkManager.

It's done analogously to ACPI/iBFT. In fact, the same ip=ibft command
line option is used, adding a more general ip=fw alias. This probably
deserves some documentation, but I'm not adding any at this time.

!257
20 jobs for lr/initrd-ofw in 88 minutes and 58 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Test
passed #585902
allowed to fail
checkpatch

00:01:59

manual #585907
allowed to fail manual
t_centos:7.5.1804
passed #585908
t_centos:7.6.1810

00:31:11

passed #585914
t_debian:10

00:23:15

passed #585913
t_debian:9

00:21:59

passed #585916
t_debian:sid

00:25:33

manual #585915
allowed to fail manual
t_debian:testing
passed #585903
t_fedora:28

00:35:47

failed #588027
t_fedora:29

00:48:34

passed #585905
t_fedora:30

00:40:21

manual #585906
allowed to fail manual
t_fedora:rawhide
passed #585909
t_ubuntu:16.04

00:26:44

passed #585910
t_ubuntu:18.04

00:26:06

manual #585912
allowed to fail manual
t_ubuntu:devel
manual #585911
allowed to fail manual
t_ubuntu:rolling
failed #587960
t_fedora:29

00:47:52

failed #587510
t_fedora:29

00:39:39

failed #585904
t_fedora:29

00:47:59

 
  External
failed https://desktopqe-jenkins.rhev-ci-vms.eng.rdu2.redhat.com/job/beaker-NetworkManager-gitlab-trigger-code-upstream/682/

failed https://desktopqe-jenkins.rhev-ci-vms.eng.rdu2.redhat.com/job/beaker-NetworkManager-gitlab-trigger-code-upstream/682/

00:33:22

 
Name Stage Failure
failed
t_fedora:29 Test
make[3]: *** [Makefile:17420: check-am] Error 2
make[3]: Leaving directory '/builds/NetworkManager/NetworkManager/NetworkManager-1.21.1/_build/sub'
make[2]: *** [Makefile:16637: check-recursive] Error 1
make[2]: Leaving directory '/builds/NetworkManager/NetworkManager/NetworkManager-1.21.1/_build/sub'
make[1]: *** [Makefile:17422: check] Error 2
make[1]: Leaving directory '/builds/NetworkManager/NetworkManager/NetworkManager-1.21.1/_build/sub'
make: *** [Makefile:17342: distcheck] Error 1
Error make distcheck
ERROR: Job failed: exit code 1