u-boot: add a boot command to boot using both ramdisk and nfs

This is used for some debian network boot that uses a ramdisk to load the right
module before mounting the nfs rootfs.

Signed-off-by: Rémi Duraffort <remi.duraffort@linaro.org>
15 jobs for issue_256 in 9 minutes and 48 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Test
passed #39534
amd64
dispatcher-debian-10

00:03:22

passed #39532
amd64
dispatcher-debian-9

00:03:27

passed #39535
amd64
server-debian-10

00:03:10

passed #39533
amd64
server-debian-9

00:03:31

 
  Analyze
passed #39537
amd64
black

00:00:33

passed #39539
amd64
code_quality

00:00:27

passed #39538
amd64
codestyle

00:00:41

passed #39541
amd64
job-schema

00:00:43

passed #39540
amd64
pylint

00:02:17

passed #39536
dind amd64 allowed to fail
sast

00:02:14

 
  Build
passed #39544
amd64
amd64/pkg-debian-10

00:01:34

passed #39543
amd64
amd64/pkg-debian-9

00:01:47

passed #39542
amd64
doc

00:01:21

 
  Docker
passed #39545
dind amd64
amd64/lava-dispatcher

00:00:44

passed #39546
dind amd64
amd64/lava-server

00:02:12