drm: Implement O_NONBLOCK support on /dev/dri/cardN
(bnc#904097).

suse-commit: 15eeb8b671f94330af3c2949ce22bbf4f8c4deba
drm/i915: Keep vblank interrupts enabled while
enabling/disabling planes (bnc#904097).

suse-commit: 6ba27fbe6ffb9f0bb436aea0c22018a63d663817