drm/msm/dpu: Remove dpu_dbg

The functions in dpu_dbg.c aren't used. The two main dump functions
fail after a lookup from dpu_dbg_base.reg_base_list which turns out
to never be populated and once those are removed the rest of the
file doesn't make any sense.

v3: No changes
v2: Moved some unrelated changes to another patch

Reviewed-by: Sean Paul <sean@poorly.run>
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>