rework etna_screen_get_name(..)

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
port etna_screen to libdrm-etnaviv (compile tested only)

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
rework etna_drm_screen_create(..)

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>