msm: kgsl: Add an helper function to read DT properties

Now that we are transitioning away from non DT enabled targets we
will start reading properties as needed instead of storing them
in a large struct. This function will do the appropriate
translations for reading an u32 property from the root DT node for
the device.

Change-Id: Ic0dedbad1a8d53a0c50030e55d124969d25a612f
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>