drm/msm: move debugfs registration to late_register callbacks

Need to move debugfs registration into the appropriate callbacks
that get called after the device is registered. Debugfs root
nodes are only called after drm_dev_register. After that, kms
needs to implement the postinit callback to register debugfs,
and drm components like crtc, connector, encoder must implement
the late_register and early_unregister callbacks to properly
add debugfs entries.

Change-Id: I862ca3b8fa0b813b36278ac9bbaebbcdcd2d58df
Signed-off-by: Lloyd Atkinson <latkinso@codeaurora.org>