sh: use shared frequency tables on sh7785

This patch converts the sh7785 clock code to make use
of clk_rate_table_build() and clk_rate_table_round().
The ->build_rate_table() callback is removed, the
table building is instead handled in ->recalc().

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>