main/linux-vanilla: fix /boot/dtbs directory

install dtbs under /boot/dtbs instead of /boot/dtbs/$_abi_release
so the u-boot can find it without need to fix/change DEVICETREEDIR
in extlinux.conf on every kernel upgrade

This will work until we made versioned kernel upgrade and preserve
previous kernel version on upgrade
13 jobs for !290 with linux-vanilla-fix-dtbs-dir in 91 minutes and 2 seconds (queued for 2 seconds)
detached
Status Job ID Name Coverage
  Lint
failed #2248
docker-alpine x86_64 allowed to fail
lint

00:00:18

 
  Build
passed #2252
docker-alpine ci-build ppc64le
build-ppc64le

00:04:53

passed #2251
docker-alpine ci-build s390x
build-s390x

00:12:29

failed #2254
x86 ci-build docker-alpine
build-x86

01:00:01

passed #2378
x86_64 ci-build docker-alpine
build-x86_64

00:18:12

failed #2250
docker-alpine ci-build x86
build-x86

01:00:00

failed #2376
x86_64 ci-build docker-alpine
build-x86_64

00:19:18

failed #2253
x86_64 ci-build docker-alpine
build-x86_64

01:00:00

failed #2377
docker-alpine ci-build x86_64
build-x86_64

00:18:00

failed #2255
docker-alpine ci-build x86_64
build-x86_64

01:52:23

failed #2249
docker-alpine ci-build x86_64
build-x86_64

01:00:00

canceled #2375
docker-alpine ci-build x86_64
build-x86_64

00:07:19

canceled #2271
x86_64 ci-build docker-alpine
build-x86_64

01:02:46

 
Name Stage Failure
failed
build-x86 Build The script exceeded the maximum execution time set for the job
No job log
failed
lint Lint
No job log