drm/msm: Only add available components

When trying to get the display up on my sdm845 board I noticed that
the display wouldn't probe if I had the dsi1 node marked as "disabled"
even though my board doesn't use dsi1.  It looks like the msm code
adds all nodes to its list of components even if they are disabled.  I
believe this doesn't work because all registered components need to
come up before we finish probing.  Let's do like other DRM code and
only add available components.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Rob Clark <robdclark@gmail.com>