clk: renesas: rcar-gen3: Pass name/offset to cpg_sd_clk_register()
Explicitly pass the clock's name and register offset to
cpg_sd_clk_register(), so the latter doesn't have to extract them from
the cpg_core_clk object.
This keeps all cpg_core_clk parsing and unmarshalling contained in a
single function (rcar_gen3_cpg_clk_register()).