drm/msm/dpu: add support for clk and bw scaling for display

This change adds support to scale src clk and bandwidth as
per composition requirements.

Interconnect registration for bw has been moved to mdp
device node from mdss to facilitate the scaling.

Changes in v1:
 - Address armv7 compilation issues with the patch (Rob)

Signed-off-by: Kalyan Thota <kalyan_t@codeaurora.org>
Reviewed-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>