vfb: factor out method to add a crtc

3 jobs for vfb-add_crtc in 4 minutes and 36 seconds (queued for 4 seconds)
latest
Status Name Job ID Coverage
  Docker Image
passed debian-testing #437657

00:00:22

 
  Build And Test
passed autotools-build-and-test #437658

00:04:13

passed meson-build-and-test #437659

00:02:14