sh: clkfwk: sh_clk_init_parent() should be called after clk_register()

sh_clk_init_parent() are using clk->mapped_reg
which is mapped in clk_register()

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>