ARM: OMAP: Convert __clk_get_rate() to provider/consumer APIs

We're removing struct clk from the clk provider API, so switch to
clk_get_rate() and clk_hw_get_rate() here appropriately.

Acked-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>