drm/msm: dpu: Move crtc runtime resume to encoder

The crtc runtime resume doesn't actually operate on the crtc, but rather
its encoders. The problem with this is that we need to inspect the crtc
state to get the currently connected encoders. Since runtime resume
isn't guaranteed to be called while holding the modeset locks (although
it sometimes is), this presents a race condition.

Now that we have ->enabled on the virtual encoders, and a lock to
protect it, just call resume on each encoder and only restore the ones
that are enabled.

Changes in v2:
- None

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

Signed-off-by: Rob Clark <robdclark@gmail.com>