drm/msm/dpu: map mixer/ctl hw blocks in encoder modeset

drm/msm/dpu: map mixer/ctl hw blocks in encoder modeset

After resource allocation, iterate and populate mixer/ctl
hw blocks in encoder modeset thereby centralizing all
the resource mapping to the CRTC. This change is made
for easy switching to state based allocation using
private objects later in this series.

Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1550107156-17625-6-git-send-email-jsanka@codeaurora.org
Signed-off-by: Rob Clark <robdclark@chromium.org>