sh: Add div6_reparent_clks to clock framework for FSI

Current clk_ops doesn't support .init which
is used to select external clock on ecovec
without CONFIG_SH_CLK_CPG_LEGACY.
To solve this problem, this patch add div6_reparent_clks
to clock-sh7724.
This patch solve compile error too.

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