drm/msm/mdp5: Add cursor planes

Register cursor drm_planes. The loop in modeset_init that inits the
planes and crtcs has to be refactored a bit. We first iterate all the
hwpipes to find the cursor planes. Then, we loop again to create
crtcs.

In msm_atomic_wait_for_commit_done, remove the check which bypasses
waiting for vsyncs if state->legacy_cursor_updates is true.

We will later create a fast path for cursor position changes in the
cursor plane's update_plane func that doesn't go via the regular
atomic commit path. For rest of cursor related updates, we will have
to wait for vsyncs, so ignore the legacy_cursor_updates flag.

Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>