backends: force enable modifiers on tagged devices

Some devices can't scanout to linear buffers directly as the hw is not
capable of eg rendering into a linear depth buffer.

Add code to force kms-modifiers on udev taged devices.

Closes: GNOME/mutter#1408

GNOME/mutter!1443
6 jobs for !1443 with tegra in 8 minutes and 8 seconds (queued for 3 seconds)
detached
Status Job ID Name Coverage
  Review
passed #902355
check-commit-log

00:00:16

 
  Build
passed #902356
build-mutter

00:03:32

passed #902358
build-without-native-backend-and-wayland

00:02:04

passed #902357
build-without-opengl-and-glx

00:03:06

 
  Test
passed #902360
can-build-gnome-shell

00:01:34

passed #902359
test-mutter

00:04:35