drm/msm/dpu: remove struct encoder_kickoff_params

The contents of struct encoder_kickoff_params are never used. Remove the
structure and all remnants of it from function calls.

Changes in v2 (seanpaul):
- Actually remove the struct (Jeykumar)

Cc: Jeykumar Sankaran <jsanka@codeaurora.org>
Signed-off-by: Bruce Wang <bzwang@chromium.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>