clk: qcom: mdss: update PLL resources based on ref count

At present, the PLL resources are updated based on the
enable/disable parameter that is passed to the API. Add
support to update the PLL resources based on a ref count.
This avoids additional delay due to repeated enable/disable
of the resources and also maintains proper state of the PLL
resources.

Change-Id: I39b7ee2b33acb81acdb7dc1f4f387dc71381a464
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>