sh: sh7723 clock framework rewrite V2

This patch contains V2 of the sh7723 clock framework
rewrite. 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>