vfb: factor out method to add a crtc

3 jobs for vfb-add_crtc in 12 minutes and 29 seconds (queued for 16 minutes and 59 seconds)
Status Job ID Name Coverage
  Docker Image
passed #428475
debian-testing

00:00:33

 
  Build And Test
passed #428476
autotools-build-and-test

00:07:52

passed #428477
meson-build-and-test

00:04:03