clk: highbank: Migrate to clk_hw based registration and OF APIs

Now that we have clk_hw based provider APIs to register clks, we
can get rid of struct clk pointers in this driver, allowing us to
move closer to a clear split of consumer and provider clk APIs.

Signed-off-by: Stephen Boyd <stephen.boyd@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>