Check for AMDGPU_CREATE_PIXMAP_SCANOUT in amdgpu_glamor_create_pixmap

We must not call glamor_create_pixmap or fbCreatePixmap when it's set.

Closes: #21
12 jobs for master in 1 minute and 10 seconds (queued for 6 seconds)
Status Job ID Name Coverage
  Docker Image
passed #4538628
container-build

00:00:16

 
  Build
passed #4538631
xserver-1.13

00:00:39

passed #4538632
xserver-1.14

00:00:49

passed #4538633
xserver-1.15

00:00:39

passed #4538634
xserver-1.16

00:00:49

passed #4538635
xserver-1.17

00:00:40

passed #4538636
xserver-1.18

00:00:48

passed #4538637
xserver-1.18-clang

00:00:43

passed #4538638
xserver-1.19

00:00:49

passed #4538639
xserver-1.19-clang

00:00:28

passed #4538629
xserver-1.20

00:00:52

passed #4538630
xserver-1.20-clang

00:00:54