dm: test: clk: Add test for ccf clk_set_rate()

test: dm: clk_ccf: fix building error

test: dm: clk_ccf: test ccf_clk_ops

clk: Check that composite clock's div has set_rate()

clk: get correct ops for clk_enable() and clk_disable()

clk: check parent_name in clk_register to avoid confusing log_error() output

clk: also handle ENOENT in *_optional functions

clk: use private clk struct in CLK_CCF's enable/disable functions