sh: sh7343 clock framework rewrite

This patch rewrites the sh7343 clock framework code.
The new code makes use of the recently merged div4,
div6 and mstp32 helper code. Both extal and dll are
supported as input clocks to the pll.

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