qt-multi-screen-compositor:mx6: Enable linux-dmabuf-unstable-v1

Enabling linux-dmabuf-unstable-v1 fixes the distorted visualization
on imx6 devices.

See https://codereview.qt-project.org/c/qt/qtwayland/+/214050

BCS 746-000838

recipes-qt/qt-multi-screen-compositor/files/qt-multi-screen-compositor.service

@@ -21,6 +21,9 @@ Environment=QT_QPA_PLATFORM=eglfs
 Environment=QT_QPA_EGLFS_INTEGRATION=eglfs_kms
 Environment=QT_QPA_EGLFS_KMS_ATOMIC=1
 
+Environment=QT_WAYLAND_CLIENT_BUFFER_INTEGRATION=linux-dmabuf-unstable-v1
+Environment=QT_WAYLAND_SERVER_BUFFER_INTEGRATION=dmabuf-server
+
 # The following parameter rotates the touchscreen input
 # by 180 degrees. As the normal libinput calibration isn't
 # implemented yet, this is the only way to enable touch