drm: Nuke drm_atomic_helper_crtc_set_property

It's dead code because this is now handled in the core.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: David Airlie <airlied@linux.ie>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Shawn Guo <shawn.guo@linaro.org>
Cc: Eric Engestrom <eric@engestrom.ch>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Philippe Cornu <philippe.cornu@st.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Sushmita Susheelendra <ssusheel@codeaurora.org>
Cc: Archit Taneja <architt@codeaurora.org>
Cc: intel-gfx@lists.freedesktop.org
Cc: nouveau@lists.freedesktop.org
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170725080122.20548-5-daniel.vetter@ffwll.ch
Reviewed-by: Archit Taneja <architt@codeaurora.org>
Acked-by: Philippe Cornu <philippe.cornu@st.com>
Tested-by: Philippe Cornu <philippe.cornu@st.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Acked-by: Thomas Hellstrom <thellstrom@vmware.com>