drm: Refactor setplane to allow internal use (v3)

Refactor DRM setplane code into a new setplane_internal() function that
takes DRM objects directly as parameters rather than looking them up by
ID.  We'll use this in a future patch when we implement legacy cursor
ioctls on top of the universal plane interface.

v3:
 - Move integer overflow checking from setplane_internal to setplane
   ioctl.  The upcoming legacy cursor support via universal planes needs
   to maintain current cursor ioctl semantics and not return error for
   these extreme values (found via intel-gpu-tools kms_cursor_crc test).
v2:
 - Allow planes to be disabled without a valid crtc again (and add
   mention of this to setplane's kerneldoc, since it doesn't seem to be
   mentioned anywhere else).
 - Reformat some parameter line wrap

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Pallavi G<pallavi.g@intel.com>
Acked-by: Dave Airlie <airlied@linux.ie>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --cc drivers/gpu/drm/drm_crtc.c
Simple merge