drm/i915: Switch to unified plane cursor handling (v4)

drm/i915: Switch to unified plane cursor handling (v4)

The DRM core will translate calls to legacy cursor ioctls into universal
cursor calls automatically, so there's no need to maintain the legacy
cursor support.  This greatly simplifies the transition since we don't
have to handle reference counting differently depending on which cursor
interface was called.

The aim here is to transition to the universal plane interface with
minimal code change.  There's a lot of cleanup that can be done (e.g.,
using state stored in crtc->cursor->fb rather than intel_crtc) that is
left to future patches.

v4:
 - Drop drm_gem_object_unreference() that is no longer needed now that
   we receive the GEM obj directly rather than looking up the ID.
v3:
 - Pass cursor obj to intel_crtc_cursor_set_obj() if cursor fb changes,
   even if 'visible' is false.  intel_crtc_cursor_set_obj() will notice
   that the cursor isn't visible and disable it properly, but we still
   need to get intel_crtc->cursor_addr set properly so that we behave
   properly if the cursor becomes visible again in the future without
   changing the cursor buffer (noted by Chris Wilson and verified
   via i-g-t kms_cursor_crc).
 - s/drm_plane_init/drm_universal_plane_init/.  Due to type
   compatibility between enum and bool, everything actually works
   correctly with the wrong init call, except for the type of plane that
   gets exposed to userspace (it shows up as type 'primary' rather than
   type 'cursor').
v2:
 - Remove duplicate dimension checks on cursor
 - Drop explicit cursor disable from crtc destroy (fb & plane
   destruction will take care of that now)
 - Use DRM plane helper to check update parameters

Cc: intel-gfx@lists.freedesktop.org
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Pallavi G<pallavi.g@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>