clk: qcom: clk-dummy: convert into a platform driver

Modify the clk-dummy driver so that it registers a platform
driver instead of using CLK_OF_DECLARE().  This is needed for
device struct based dependency tracking to work properly.

Change-Id: I545c6e6a11e349e6eec0c75c106932d3909c54c8
Signed-off-by: David Collins <collinsd@codeaurora.org>