clk: sunxi: Convert to clk_hw based provider APIs

We're removing struct clk from the clk provider API, so switch
this code to using the clk_hw based provider APIs.

Cc: Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: "Emilio López" <emilio@elopez.com.ar>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>