drm/msm/disp/dpu: Remove unused code from drm_crtc.c

Remove a chunk of unused code from drm_crtc.c, namely
dpu_crtc_res_add, dpu_crtc_res_get, dpu_crtc_res_put
and associated static functions.

Also zap dpu_crtc_event_queue(), helper functions
and members.

Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>