output/kms: Use meta_kms_connector_get_preferred_mode in init_output_modes
I have a monitor which can report two preferred modes: 5120x1440@240 and 3840x1080@60. Since they are enumerated in this order by KMS, init_output_modes would end up using 3840x1080@60 (and it was impossible to select any 5120x1440 mode in the GNOME display settings).
Fix this by using meta_kms_connector_get_preferred_mode, which returns the first KMS mode with DRM_MODE_TYPE_PREFERRED.
Edited by Michel Dänzer