drm/msm/dp: move debugfs node to /sys/kernel/debug/dri/*/

Move the MSM DP debugfs node from /sys/kernel/debug/drm_dp
to /sys/kernel/debug/dri/*/ as required for video pattern
compliance test suite.

Changes in v2: rebase on top of latest patchset of dependency

Signed-off-by: Abhinav Kumar <abhinavk@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>